[Python-checkins] Overhaul datetime documentation (GH-13410)
Miss Islington (bot)
webhook-mailer at python.org
Thu Sep 12 10:37:40 EDT 2019
https://github.com/python/cpython/commit/8976359c598f56825648f4e5397b78c5d14ea13c
commit: 8976359c598f56825648f4e5397b78c5d14ea13c
branch: 3.8
author: Miss Islington (bot) <31488909+miss-islington at users.noreply.github.com>
committer: GitHub <noreply at github.com>
date: 2019-09-12T07:37:36-07:00
summary:
Overhaul datetime documentation (GH-13410)
This is a restructuring of the datetime documentation to hopefully make
them more user-friendly and approachable to new users without losing any
of the detail.
Changes include:
- Creating dedicated subsections for some concepts such as:
- "Constants"
- "Naive vs Aware"
- "Determining if an Object is Aware"
- Give 'naive vs aware' its own subsection
- Give 'constants' their own subsection
- Overhauling the strftime-strptime section by:
- Breaking it into logical, linkable, and digestable parts
- Adding a high-level comparison table
- Moving the technical detail to bottom: readers come to this
section primarily to remind themselves to things:
- How do I write the format code for X?
- strptime/strftime: which one is which again?
- Touching up fromisoformat + isoformat sections by:
- Revising fromisoformat + isoformat for date, time, and
datetime
- Adding basic examples
- Enforcing consistency about putting formats (i.e. ``HH:MM``)
in double backticks. This was previously done in some places
but not all
- Putting long 'supported formats', on their own line to improve
readability
- Moving the 'seealso' section to the top and add a link to dateutil
Rationale: This doesn't really belong nested under the
'constants' section. Let readers know right away that
datetime is one of several related tools.
- Moving common features of several types into one place:
Previously, each type went out of its way to note separately
that it was hashable and picklable. These can be brought
into one single place that is more prominent.
- Reducing some verbose explanations to improve readability
- Breaking up long paragraphs into digestable chunks
- Displaying longer "equivalent to" examples, as short code blocks
- Using the dot notation for datetime/time classes:
Use :class:`.time` and :class:`.datetime` rather than :class:`time` and
:class:`datetime`; otherwise, the generated links will route to the
respective modules, not classes.
- Rewording the tzinfo class description
The top paragraph should get straight to the point of telling the reader
what subclasses of tzinfo _do_. Previously, that was hidden in a later
paragraph.
- Adding a note on .today() versus .now()
- Rearranging and expanding example blocks, including:
- Moved long, multiline inline examples to standalone examples
- Simplified the example block for timedelta arithmetic:
- Broke the example into two logical sections:
1. normalization/parameter 'merging'
2. timedelta arithmetic
- Reduced the complexity of the some of the examples. Show
reasonable, real-world uses cases that are easy to follow
along with and progres in difficult slightly.
- Broke up the example sections for date and datetime sections by putting
the easy examples first, progressing to more esoteric situations and
breaking it up into logical sections based on what the methods are
doing at a high level.
- Simplified the KabulTz example:
- Put the class definition itself into a non-REPL block since there is
no interactive output involved there
- Briefly explained what's happening before launching into the code
- Broke the example section into visually separate chunks
- Various whitespace, formatting, style and grammar fixes including:
- Consistently using backctics for 'date_string' formats
- Consistently using one space after periods.
- Consistently using bold for vocab terms
- Consistently using italics when referring to params:
See https://devguide.python.org/documenting/GH-id4
- Using '::' to lead into code blocks
Per https://devguide.python.org/documenting/GH-source-code, this will
let the reader use the 'expand/collapse' top-right button for REPL
blocks to hide or show the prompt.
- Using consistent captialization schemes
- Removing use of the default role
- Put 'example' blocks in Markdown subsections
This is a combination of 66 commits.
See bpo-36960: https://bugs.python.org/issue36960
(cherry picked from commit 3fb1363fe87a24cdb2ee1dd9746f1c49046af958)
Co-authored-by: Brad <brad.solomon.1124 at gmail.com>
files:
A Misc/NEWS.d/next/Documentation/2019-05-18-16-25-44.bpo-36960.xEKHXj.rst
M Doc/library/datetime.rst
diff --git a/Doc/library/datetime.rst b/Doc/library/datetime.rst
index 50f1b9e74949..882d4e16e1f6 100644
--- a/Doc/library/datetime.rst
+++ b/Doc/library/datetime.rst
@@ -14,40 +14,59 @@
.. XXX what order should the types be discussed in?
-The :mod:`datetime` module supplies classes for manipulating dates and times in
-both simple and complex ways. While date and time arithmetic is supported, the
-focus of the implementation is on efficient attribute extraction for output
-formatting and manipulation. For related functionality, see also the
-:mod:`time` and :mod:`calendar` modules.
-
-There are two kinds of date and time objects: "naive" and "aware".
-
-An aware object has sufficient knowledge of applicable algorithmic and
-political time adjustments, such as time zone and daylight saving time
-information, to locate itself relative to other aware objects. An aware object
-is used to represent a specific moment in time that is not open to
-interpretation [#]_.
-
-A naive object does not contain enough information to unambiguously locate
-itself relative to other date/time objects. Whether a naive object represents
+The :mod:`datetime` module supplies classes for manipulating dates and times.
+
+While date and time arithmetic is supported, the focus of the implementation is
+on efficient attribute extraction for output formatting and manipulation.
+
+.. seealso::
+
+ Module :mod:`calendar`
+ General calendar related functions.
+
+ Module :mod:`time`
+ Time access and conversions.
+
+ Package `dateutil <https://dateutil.readthedocs.io/en/stable/>`_
+ Third-party library with expanded time zone and parsing support.
+
+.. _datetime-naive-aware:
+
+Aware and Naive Objects
+-----------------------
+
+Date and time objects may be categorized as "aware" or "naive."
+
+With sufficient knowledge of applicable algorithmic and political time
+adjustments, such as time zone and daylight saving time information,
+an **aware** object can locate itself relative to other aware objects.
+An aware object represents a specific moment in time that is not open to
+interpretation. [#]_
+
+A **naive** object does not contain enough information to unambiguously locate
+itself relative to other date/time objects. Whether a naive object represents
Coordinated Universal Time (UTC), local time, or time in some other timezone is
purely up to the program, just like it is up to the program whether a
-particular number represents metres, miles, or mass. Naive objects are easy to
+particular number represents metres, miles, or mass. Naive objects are easy to
understand and to work with, at the cost of ignoring some aspects of reality.
For applications requiring aware objects, :class:`.datetime` and :class:`.time`
objects have an optional time zone information attribute, :attr:`!tzinfo`, that
can be set to an instance of a subclass of the abstract :class:`tzinfo` class.
These :class:`tzinfo` objects capture information about the offset from UTC
-time, the time zone name, and whether Daylight Saving Time is in effect. Note
-that only one concrete :class:`tzinfo` class, the :class:`timezone` class, is
-supplied by the :mod:`datetime` module. The :class:`timezone` class can
-represent simple timezones with fixed offset from UTC, such as UTC itself or
-North American EST and EDT timezones. Supporting timezones at deeper levels of
-detail is up to the application. The rules for time adjustment across the
+time, the time zone name, and whether daylight saving time is in effect.
+
+Only one concrete :class:`tzinfo` class, the :class:`timezone` class, is
+supplied by the :mod:`datetime` module. The :class:`timezone` class can
+represent simple timezones with fixed offsets from UTC, such as UTC itself or
+North American EST and EDT timezones. Supporting timezones at deeper levels of
+detail is up to the application. The rules for time adjustment across the
world are more political than rational, change frequently, and there is no
standard suitable for every application aside from UTC.
+Constants
+---------
+
The :mod:`datetime` module exports the following constants:
.. data:: MINYEAR
@@ -61,16 +80,6 @@ The :mod:`datetime` module exports the following constants:
The largest year number allowed in a :class:`date` or :class:`.datetime` object.
:const:`MAXYEAR` is ``9999``.
-
-.. seealso::
-
- Module :mod:`calendar`
- General calendar related functions.
-
- Module :mod:`time`
- Time access and conversions.
-
-
Available Types
---------------
@@ -86,7 +95,7 @@ Available Types
:noindex:
An idealized time, independent of any particular day, assuming that every day
- has exactly 24\*60\*60 seconds (there is no notion of "leap seconds" here).
+ has exactly 24\*60\*60 seconds. (There is no notion of "leap seconds" here.)
Attributes: :attr:`hour`, :attr:`minute`, :attr:`second`, :attr:`microsecond`,
and :attr:`.tzinfo`.
@@ -109,7 +118,7 @@ Available Types
.. class:: tzinfo
:noindex:
- An abstract base class for time zone information objects. These are used by the
+ An abstract base class for time zone information objects. These are used by the
:class:`.datetime` and :class:`.time` classes to provide a customizable notion of
time adjustment (for example, to account for time zone and/or daylight saving
time).
@@ -122,22 +131,8 @@ Available Types
.. versionadded:: 3.2
-
Objects of these types are immutable.
-Objects of the :class:`date` type are always naive.
-
-An object of type :class:`.time` or :class:`.datetime` may be naive or aware.
-A :class:`.datetime` object *d* is aware if ``d.tzinfo`` is not ``None`` and
-``d.tzinfo.utcoffset(d)`` does not return ``None``. If ``d.tzinfo`` is
-``None``, or if ``d.tzinfo`` is not ``None`` but ``d.tzinfo.utcoffset(d)``
-returns ``None``, *d* is naive. A :class:`.time` object *t* is aware
-if ``t.tzinfo`` is not ``None`` and ``t.tzinfo.utcoffset(None)`` does not return
-``None``. Otherwise, *t* is naive.
-
-The distinction between naive and aware doesn't apply to :class:`timedelta`
-objects.
-
Subclass relationships::
object
@@ -148,6 +143,40 @@ Subclass relationships::
date
datetime
+Common Properties
+^^^^^^^^^^^^^^^^^
+
+The :class:`date`, :class:`.datetime`, :class:`.time`, and :class:`timezone` types
+share these common features:
+
+- Objects of these types are immutable.
+- Objects of these types are hashable, meaning that they can be used as
+ dictionary keys.
+- Objects of these types support efficient pickling via the :mod:`pickle` module.
+
+Determining if an Object is Aware or Naive
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Objects of the :class:`date` type are always naive.
+
+An object of type :class:`.time` or :class:`.datetime` may be aware or naive.
+
+A :class:`.datetime` object *d* is aware if both of the following hold:
+
+1. ``d.tzinfo`` is not ``None``
+2. ``d.tzinfo.utcoffset(d)`` does not return ``None``
+
+Otherwise, *d* is naive.
+
+A :class:`.time` object *t* is aware if both of the following hold:
+
+1. ``t.tzinfo`` is not ``None``
+2. ``t.tzinfo.utcoffset(None)`` does not return ``None``.
+
+Otherwise, *t* is naive.
+
+The distinction between aware and naive doesn't apply to :class:`timedelta`
+objects.
.. _datetime-timedelta:
@@ -159,11 +188,11 @@ dates or times.
.. class:: timedelta(days=0, seconds=0, microseconds=0, milliseconds=0, minutes=0, hours=0, weeks=0)
- All arguments are optional and default to ``0``. Arguments may be integers
+ All arguments are optional and default to ``0``. Arguments may be integers
or floats, and may be positive or negative.
- Only *days*, *seconds* and *microseconds* are stored internally. Arguments are
- converted to those units:
+ Only *days*, *seconds* and *microseconds* are stored internally.
+ Arguments are converted to those units:
* A millisecond is converted to 1000 microseconds.
* A minute is converted to 60 seconds.
@@ -177,10 +206,28 @@ dates or times.
* ``0 <= seconds < 3600*24`` (the number of seconds in one day)
* ``-999999999 <= days <= 999999999``
+ The following example illustrates how any arguments besides
+ *days*, *seconds* and *microseconds* are "merged" and normalized into those
+ three resulting attributes::
+
+ >>> from datetime import timedelta
+ >>> delta = timedelta(
+ ... days=50,
+ ... seconds=27,
+ ... microseconds=10,
+ ... milliseconds=29000,
+ ... minutes=5,
+ ... hours=8,
+ ... weeks=2
+ ... )
+ >>> # Only days, seconds, and microseconds remain
+ >>> delta
+ datetime.timedelta(days=64, seconds=29156, microseconds=10)
+
If any argument is a float and there are fractional microseconds,
the fractional microseconds left over from all arguments are
combined and their sum is rounded to the nearest microsecond using
- round-half-to-even tiebreaker. If no argument is a float, the
+ round-half-to-even tiebreaker. If no argument is a float, the
conversion and normalization processes are exact (no information is
lost).
@@ -188,7 +235,7 @@ dates or times.
:exc:`OverflowError` is raised.
Note that normalization of negative values may be surprising at first. For
- example,
+ example::
>>> from datetime import timedelta
>>> d = timedelta(microseconds=-1)
@@ -196,7 +243,7 @@ dates or times.
(-1, 86399, 999999)
-Class attributes are:
+Class attributes:
.. attribute:: timedelta.min
@@ -263,7 +310,7 @@ Supported operations:
| | timedelta.resolution using round-half-to-even.|
+--------------------------------+-----------------------------------------------+
| ``t1 = t2 // i`` or | The floor is computed and the remainder (if |
-| ``t1 = t2 // t3`` | any) is thrown away. In the second case, an |
+| ``t1 = t2 // t3`` | any) is thrown away. In the second case, an |
| | integer is returned. (3) |
+--------------------------------+-----------------------------------------------+
| ``t1 = t2 % t3`` | The remainder is computed as a |
@@ -282,8 +329,8 @@ Supported operations:
| | -*t1.seconds*, -*t1.microseconds*), |
| | and to *t1*\* -1. (1)(4) |
+--------------------------------+-----------------------------------------------+
-| ``abs(t)`` | equivalent to +\ *t* when ``t.days >= 0``, and|
-| | to -*t* when ``t.days < 0``. (2) |
+| ``abs(t)`` | equivalent to +\ *t* when ``t.days >= 0``, |
+| | and to -*t* when ``t.days < 0``. (2) |
+--------------------------------+-----------------------------------------------+
| ``str(t)`` | Returns a string in the form |
| | ``[D day[s], ][H]H:MM:SS[.UUUUUU]``, where D |
@@ -298,10 +345,10 @@ Supported operations:
Notes:
(1)
- This is exact, but may overflow.
+ This is exact but may overflow.
(2)
- This is exact, and cannot overflow.
+ This is exact and cannot overflow.
(3)
Division by 0 raises :exc:`ZeroDivisionError`.
@@ -310,41 +357,56 @@ Notes:
-*timedelta.max* is not representable as a :class:`timedelta` object.
(5)
- String representations of :class:`timedelta` objects are normalized
- similarly to their internal representation. This leads to somewhat
- unusual results for negative timedeltas. For example:
+ String representations of :class:`timedelta` objects are normalized
+ similarly to their internal representation. This leads to somewhat
+ unusual results for negative timedeltas. For example::
- >>> timedelta(hours=-5)
- datetime.timedelta(days=-1, seconds=68400)
- >>> print(_)
- -1 day, 19:00:00
+ >>> timedelta(hours=-5)
+ datetime.timedelta(days=-1, seconds=68400)
+ >>> print(_)
+ -1 day, 19:00:00
(6)
The expression ``t2 - t3`` will always be equal to the expression ``t2 + (-t3)`` except
when t3 is equal to ``timedelta.max``; in that case the former will produce a result
while the latter will overflow.
-In addition to the operations listed above :class:`timedelta` objects support
+In addition to the operations listed above, :class:`timedelta` objects support
certain additions and subtractions with :class:`date` and :class:`.datetime`
objects (see below).
.. versionchanged:: 3.2
Floor division and true division of a :class:`timedelta` object by another
:class:`timedelta` object are now supported, as are remainder operations and
- the :func:`divmod` function. True division and multiplication of a
+ the :func:`divmod` function. True division and multiplication of a
:class:`timedelta` object by a :class:`float` object are now supported.
-Comparisons of :class:`timedelta` objects are supported with the
-:class:`timedelta` object representing the smaller duration considered to be the
-smaller timedelta. In order to stop mixed-type comparisons from falling back to
-the default comparison by object address, when a :class:`timedelta` object is
-compared to an object of a different type, :exc:`TypeError` is raised unless the
-comparison is ``==`` or ``!=``. The latter cases return :const:`False` or
-:const:`True`, respectively.
+Comparisons of :class:`timedelta` objects are supported, with some caveats.
+
+The comparisons ``==`` or ``!=`` *always* return a :class:`bool`, no matter
+the type of the compared object::
-:class:`timedelta` objects are :term:`hashable` (usable as dictionary keys), support
-efficient pickling, and in Boolean contexts, a :class:`timedelta` object is
+ >>> from datetime import timedelta
+ >>> delta1 = timedelta(seconds=57)
+ >>> delta2 = timedelta(hours=25, seconds=2)
+ >>> delta2 != delta1
+ True
+ >>> delta2 == 5
+ False
+
+For all other comparisons (such as ``<`` and ``>``), when a :class:`timedelta`
+object is compared to an object of a different type, :exc:`TypeError`
+is raised::
+
+ >>> delta2 > delta1
+ True
+ >>> delta2 > 5
+ Traceback (most recent call last):
+ File "<stdin>", line 1, in <module>
+ TypeError: '>' not supported between instances of 'datetime.timedelta' and 'int'
+
+In Boolean contexts, a :class:`timedelta` object is
considered to be true if and only if it isn't equal to ``timedelta(0)``.
Instance methods:
@@ -360,29 +422,36 @@ Instance methods:
.. versionadded:: 3.2
+Examples of usage: :class:`timedelta`
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-Example usage:
+An additional example of normalization::
+ >>> # Components of another_year add up to exactly 365 days
>>> from datetime import timedelta
>>> year = timedelta(days=365)
>>> another_year = timedelta(weeks=40, days=84, hours=23,
- ... minutes=50, seconds=600) # adds up to 365 days
- >>> year.total_seconds()
- 31536000.0
+ ... minutes=50, seconds=600)
>>> year == another_year
True
+ >>> year.total_seconds()
+ 31536000.0
+
+Examples of :class:`timedelta` arithmetic::
+
+ >>> from datetime import timedelta
+ >>> year = timedelta(days=365)
>>> ten_years = 10 * year
- >>> ten_years, ten_years.days // 365
- (datetime.timedelta(days=3650), 10)
+ >>> ten_years
+ datetime.timedelta(days=3650)
+ >>> ten_years.days // 365
+ 10
>>> nine_years = ten_years - year
- >>> nine_years, nine_years.days // 365
- (datetime.timedelta(days=3285), 9)
+ >>> nine_years
+ datetime.timedelta(days=3285)
>>> three_years = nine_years // 3
>>> three_years, three_years.days // 365
(datetime.timedelta(days=1095), 3)
- >>> abs(three_years - ten_years) == 2 * three_years + year
- True
-
.. _datetime-date:
@@ -391,17 +460,14 @@ Example usage:
A :class:`date` object represents a date (year, month and day) in an idealized
calendar, the current Gregorian calendar indefinitely extended in both
-directions. January 1 of year 1 is called day number 1, January 2 of year 1 is
-called day number 2, and so on. This matches the definition of the "proleptic
-Gregorian" calendar in Dershowitz and Reingold's book Calendrical Calculations,
-where it's the base calendar for all computations. See the book for algorithms
-for converting between proleptic Gregorian ordinals and many other calendar
-systems.
+directions.
+January 1 of year 1 is called day number 1, January 2 of year 1 is
+called day number 2, and so on. [#]_
.. class:: date(year, month, day)
- All arguments are required. Arguments must be integers in the following
+ All arguments are required. Arguments must be integers, in the following
ranges:
* ``MINYEAR <= year <= MAXYEAR``
@@ -415,17 +481,19 @@ Other constructors, all class methods:
.. classmethod:: date.today()
- Return the current local date. This is equivalent to
- ``date.fromtimestamp(time.time())``.
+ Return the current local date.
+ This is equivalent to ``date.fromtimestamp(time.time())``.
.. classmethod:: date.fromtimestamp(timestamp)
- Return the local date corresponding to the POSIX timestamp, such as is returned
- by :func:`time.time`. This may raise :exc:`OverflowError`, if the timestamp is out
- of the range of values supported by the platform C :c:func:`localtime` function,
- and :exc:`OSError` on :c:func:`localtime` failure.
- It's common for this to be restricted to years from 1970 through 2038. Note
+ Return the local date corresponding to the POSIX timestamp, such as is
+ returned by :func:`time.time`.
+
+ This may raise :exc:`OverflowError`, if the timestamp is out
+ of the range of values supported by the platform C :c:func:`localtime`
+ function, and :exc:`OSError` on :c:func:`localtime` failure.
+ It's common for this to be restricted to years from 1970 through 2038. Note
that on non-POSIX systems that include leap seconds in their notion of a
timestamp, leap seconds are ignored by :meth:`fromtimestamp`.
@@ -438,24 +506,27 @@ Other constructors, all class methods:
.. classmethod:: date.fromordinal(ordinal)
- Return the date corresponding to the proleptic Gregorian ordinal, where January
- 1 of year 1 has ordinal 1. :exc:`ValueError` is raised unless ``1 <= ordinal <=
- date.max.toordinal()``. For any date *d*, ``date.fromordinal(d.toordinal()) ==
- d``.
+ Return the date corresponding to the proleptic Gregorian ordinal, where
+ January 1 of year 1 has ordinal 1.
+
+ :exc:`ValueError` is raised unless ``1 <= ordinal <=
+ date.max.toordinal()``. For any date *d*,
+ ``date.fromordinal(d.toordinal()) == d``.
.. classmethod:: date.fromisoformat(date_string)
- Return a :class:`date` corresponding to a *date_string* in the format emitted
- by :meth:`date.isoformat`. Specifically, this function supports strings in
- the format(s) ``YYYY-MM-DD``.
+ Return a :class:`date` corresponding to a *date_string* given in the format
+ ``YYYY-MM-DD``::
- .. caution::
+ >>> from datetime import date
+ >>> date.fromisoformat('2019-12-04')
+ datetime.date(2019, 12, 4)
- This does not support parsing arbitrary ISO 8601 strings - it is only intended
- as the inverse operation of :meth:`date.isoformat`.
+ This is the inverse of :meth:`date.isoformat`. It only supports the format
+ ``YYYY-MM-DD``.
- .. versionadded:: 3.7
+ .. versionadded:: 3.7
.. classmethod:: date.fromisocalendar(year, week, day)
@@ -507,7 +578,7 @@ Supported operations:
| Operation | Result |
+===============================+==============================================+
| ``date2 = date1 + timedelta`` | *date2* is ``timedelta.days`` days removed |
-| | from *date1*. (1) |
+| | from *date1*. (1) |
+-------------------------------+----------------------------------------------+
| ``date2 = date1 - timedelta`` | Computes *date2* such that ``date2 + |
| | timedelta == date1``. (2) |
@@ -522,7 +593,7 @@ Notes:
(1)
*date2* is moved forward in time if ``timedelta.days > 0``, or backward if
- ``timedelta.days < 0``. Afterward ``date2 - date1 == timedelta.days``.
+ ``timedelta.days < 0``. Afterward ``date2 - date1 == timedelta.days``.
``timedelta.seconds`` and ``timedelta.microseconds`` are ignored.
:exc:`OverflowError` is raised if ``date2.year`` would be smaller than
:const:`MINYEAR` or larger than :const:`MAXYEAR`.
@@ -531,7 +602,7 @@ Notes:
``timedelta.seconds`` and ``timedelta.microseconds`` are ignored.
(3)
- This is exact, and cannot overflow. timedelta.seconds and
+ This is exact, and cannot overflow. timedelta.seconds and
timedelta.microseconds are 0, and date2 + timedelta == date1 after.
(4)
@@ -539,38 +610,47 @@ Notes:
date2.toordinal()``. Date comparison raises :exc:`TypeError` if
the other comparand isn't also a :class:`date` object. However,
``NotImplemented`` is returned instead if the other comparand has a
- :meth:`timetuple` attribute. This hook gives other kinds of date objects a
+ :meth:`timetuple` attribute. This hook gives other kinds of date objects a
chance at implementing mixed-type comparison. If not, when a :class:`date`
object is compared to an object of a different type, :exc:`TypeError` is raised
- unless the comparison is ``==`` or ``!=``. The latter cases return
+ unless the comparison is ``==`` or ``!=``. The latter cases return
:const:`False` or :const:`True`, respectively.
-Dates can be used as dictionary keys. In Boolean contexts, all :class:`date`
-objects are considered to be true.
+In Boolean contexts, all :class:`date` objects are considered to be true.
Instance methods:
.. method:: date.replace(year=self.year, month=self.month, day=self.day)
Return a date with the same value, except for those parameters given new
- values by whichever keyword arguments are specified. For example, if ``d ==
- date(2002, 12, 31)``, then ``d.replace(day=26) == date(2002, 12, 26)``.
+ values by whichever keyword arguments are specified.
+
+ Example::
+
+ >>> from datetime import date
+ >>> d = date(2002, 12, 31)
+ >>> d.replace(day=26)
+ datetime.date(2002, 12, 26)
.. method:: date.timetuple()
Return a :class:`time.struct_time` such as returned by :func:`time.localtime`.
- The hours, minutes and seconds are 0, and the DST flag is -1. ``d.timetuple()``
- is equivalent to ``time.struct_time((d.year, d.month, d.day, 0, 0, 0,
- d.weekday(), yday, -1))``, where ``yday = d.toordinal() - date(d.year, 1,
- 1).toordinal() + 1`` is the day number within the current year starting with
- ``1`` for January 1st.
+
+ The hours, minutes and seconds are 0, and the DST flag is -1.
+
+ ``d.timetuple()`` is equivalent to::
+
+ time.struct_time((d.year, d.month, d.day, 0, 0, 0, d.weekday(), yday, -1))
+
+ where ``yday = d.toordinal() - date(d.year, 1, 1).toordinal() + 1``
+ is the day number within the current year starting with ``1`` for January 1st.
.. method:: date.toordinal()
Return the proleptic Gregorian ordinal of the date, where January 1 of year 1
- has ordinal 1. For any :class:`date` object *d*,
+ has ordinal 1. For any :class:`date` object *d*,
``date.fromordinal(d.toordinal()) == d``.
@@ -592,26 +672,31 @@ Instance methods:
Return a 3-tuple, (ISO year, ISO week number, ISO weekday).
- The ISO calendar is a widely used variant of the Gregorian calendar. See
- https://www.staff.science.uu.nl/~gent0113/calendar/isocalendar.htm for a good
- explanation.
+ The ISO calendar is a widely used variant of the Gregorian calendar. [#]_
The ISO year consists of 52 or 53 full weeks, and where a week starts on a
- Monday and ends on a Sunday. The first week of an ISO year is the first
+ Monday and ends on a Sunday. The first week of an ISO year is the first
(Gregorian) calendar week of a year containing a Thursday. This is called week
number 1, and the ISO year of that Thursday is the same as its Gregorian year.
For example, 2004 begins on a Thursday, so the first week of ISO year 2004
- begins on Monday, 29 Dec 2003 and ends on Sunday, 4 Jan 2004, so that
- ``date(2003, 12, 29).isocalendar() == (2004, 1, 1)`` and ``date(2004, 1,
- 4).isocalendar() == (2004, 1, 7)``.
+ begins on Monday, 29 Dec 2003 and ends on Sunday, 4 Jan 2004::
+ >>> from datetime import date
+ >>> date(2003, 12, 29).isocalendar()
+ (2004, 1, 1)
+ >>> date(2004, 1, 4).isocalendar()
+ (2004, 1, 7)
.. method:: date.isoformat()
- Return a string representing the date in ISO 8601 format, 'YYYY-MM-DD'. For
- example, ``date(2002, 12, 4).isoformat() == '2002-12-04'``.
+ Return a string representing the date in ISO 8601 format, ``YYYY-MM-DD``::
+ >>> from datetime import date
+ >>> date(2002, 12, 4).isoformat()
+ '2002-12-04'
+
+ This is the inverse of :meth:`date.fromisoformat`.
.. method:: date.__str__()
@@ -620,9 +705,17 @@ Instance methods:
.. method:: date.ctime()
- Return a string representing the date, for example ``date(2002, 12,
- 4).ctime() == 'Wed Dec 4 00:00:00 2002'``. ``d.ctime()`` is equivalent to
- ``time.ctime(time.mktime(d.timetuple()))`` on platforms where the native C
+ Return a string representing the date::
+
+ >>> from datetime import date
+ >>> date(2002, 12, 4).ctime()
+ 'Wed Dec 4 00:00:00 2002'
+
+ ``d.ctime()`` is equivalent to::
+
+ time.ctime(time.mktime(d.timetuple()))
+
+ on platforms where the native C
:c:func:`ctime` function (which :func:`time.ctime` invokes, but which
:meth:`date.ctime` does not invoke) conforms to the C standard.
@@ -643,6 +736,8 @@ Instance methods:
complete list of formatting directives, see
:ref:`strftime-strptime-behavior`.
+Examples of Usage: :class:`date`
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Example of counting days to an event::
@@ -662,7 +757,7 @@ Example of counting days to an event::
>>> time_to_birthday.days
202
-Example of working with :class:`date`:
+More examples of working with :class:`date`:
.. doctest::
@@ -670,6 +765,20 @@ Example of working with :class:`date`:
>>> d = date.fromordinal(730920) # 730920th day after 1. 1. 0001
>>> d
datetime.date(2002, 3, 11)
+
+ >>> # Methods related to formatting string output
+ >>> d.isoformat()
+ '2002-03-11'
+ >>> d.strftime("%d/%m/%y")
+ '11/03/02'
+ >>> d.strftime("%A %d. %B %Y")
+ 'Monday 11. March 2002'
+ >>> d.ctime()
+ 'Mon Mar 11 00:00:00 2002'
+ >>> 'The {1} is {0:%d}, the {2} is {0:%B}.'.format(d, "day", "month")
+ 'The day is 11, the month is March.'
+
+ >>> # Methods for to extracting 'components' under different calendars
>>> t = d.timetuple()
>>> for i in t: # doctest: +SKIP
... print(i)
@@ -688,14 +797,10 @@ Example of working with :class:`date`:
2002 # ISO year
11 # ISO week number
1 # ISO day number ( 1 = Monday )
- >>> d.isoformat()
- '2002-03-11'
- >>> d.strftime("%d/%m/%y")
- '11/03/02'
- >>> d.strftime("%A %d. %B %Y")
- 'Monday 11. March 2002'
- >>> 'The {1} is {0:%d}, the {2} is {0:%B}.'.format(d, "day", "month")
- 'The day is 11, the month is March.'
+
+ >>> # A date object is immutable; all operations produce a new object
+ >>> d.replace(year=2005)
+ datetime.date(2005, 3, 11)
.. _datetime-datetime:
@@ -704,17 +809,18 @@ Example of working with :class:`date`:
--------------------------
A :class:`.datetime` object is a single object containing all the information
-from a :class:`date` object and a :class:`.time` object. Like a :class:`date`
-object, :class:`.datetime` assumes the current Gregorian calendar extended in
-both directions; like a time object, :class:`.datetime` assumes there are exactly
-3600\*24 seconds in every day.
+from a :class:`date` object and a :class:`.time` object.
+
+Like a :class:`date` object, :class:`.datetime` assumes the current Gregorian
+calendar extended in both directions; like a :class:`.time` object,
+:class:`.datetime` assumes there are exactly 3600\*24 seconds in every day.
Constructor:
.. class:: datetime(year, month, day, hour=0, minute=0, second=0, microsecond=0, tzinfo=None, *, fold=0)
- The year, month and day arguments are required. *tzinfo* may be ``None``, or an
- instance of a :class:`tzinfo` subclass. The remaining arguments must be integers
+ The *year*, *month* and *day* arguments are required. *tzinfo* may be ``None``, or an
+ instance of a :class:`tzinfo` subclass. The remaining arguments must be integers
in the following ranges:
* ``MINYEAR <= year <= MAXYEAR``,
@@ -735,31 +841,43 @@ Other constructors, all class methods:
.. classmethod:: datetime.today()
- Return the current local datetime, with :attr:`.tzinfo` ``None``. This is
- equivalent to ``datetime.fromtimestamp(time.time())``. See also :meth:`now`,
- :meth:`fromtimestamp`.
+ Return the current local datetime, with :attr:`.tzinfo` ``None``.
+
+ Equivalent to::
+
+ datetime.fromtimestamp(time.time())
+
+ See also :meth:`now`, :meth:`fromtimestamp`.
+ This method is functionally equivalent to :meth:`now`, but without a
+ ``tz`` parameter.
.. classmethod:: datetime.now(tz=None)
- Return the current local date and time. If optional argument *tz* is ``None``
+ Return the current local date and time.
+
+ If optional argument *tz* is ``None``
or not specified, this is like :meth:`today`, but, if possible, supplies more
precision than can be gotten from going through a :func:`time.time` timestamp
(for example, this may be possible on platforms supplying the C
:c:func:`gettimeofday` function).
If *tz* is not ``None``, it must be an instance of a :class:`tzinfo` subclass, and the
- current date and time are converted to *tz*’s time zone. In this case the
- result is equivalent to ``tz.fromutc(datetime.utcnow().replace(tzinfo=tz))``.
+ current date and time are converted to *tz*’s time zone. In this case the
+ result is equivalent to::
+
+ tz.fromutc(datetime.utcnow().replace(tzinfo=tz))
+
See also :meth:`today`, :meth:`utcnow`.
.. classmethod:: datetime.utcnow()
- Return the current UTC date and time, with :attr:`.tzinfo` ``None``. This is like
- :meth:`now`, but returns the current UTC date and time, as a naive
- :class:`.datetime` object. An aware current UTC datetime can be obtained by
- calling ``datetime.now(timezone.utc)``. See also :meth:`now`.
+ Return the current UTC date and time, with :attr:`.tzinfo` ``None``.
+
+ This is like :meth:`now`, but returns the current UTC date and time, as a naive
+ :class:`.datetime` object. An aware current UTC datetime can be obtained by
+ calling ``datetime.now(timezone.utc)``. See also :meth:`now`.
.. classmethod:: datetime.fromtimestamp(timestamp, tz=None)
@@ -769,9 +887,11 @@ Other constructors, all class methods:
the returned :class:`.datetime` object is naive.
If *tz* is not ``None``, it must be an instance of a :class:`tzinfo` subclass, and the
- timestamp is converted to *tz*’s time zone. In this case the result is
- equivalent to
- ``tz.fromutc(datetime.utcfromtimestamp(timestamp).replace(tzinfo=tz))``.
+ timestamp is converted to *tz*’s time zone.
+
+ In this case the result is equivalent to::
+
+ tz.fromutc(datetime.utcfromtimestamp(timestamp).replace(tzinfo=tz))
:meth:`fromtimestamp` may raise :exc:`OverflowError`, if the timestamp is out of
the range of values supported by the platform C :c:func:`localtime` or
@@ -796,7 +916,9 @@ Other constructors, all class methods:
.. classmethod:: datetime.utcfromtimestamp(timestamp)
Return the UTC :class:`.datetime` corresponding to the POSIX timestamp, with
- :attr:`.tzinfo` ``None``. This may raise :exc:`OverflowError`, if the timestamp is
+ :attr:`.tzinfo` ``None``. (The resulting object is naive.)
+
+ This may raise :exc:`OverflowError`, if the timestamp is
out of the range of values supported by the platform C :c:func:`gmtime` function,
and :exc:`OSError` on :c:func:`gmtime` failure.
It's common for this to be restricted to years in 1970 through 2038.
@@ -824,7 +946,7 @@ Other constructors, all class methods:
Return the :class:`.datetime` corresponding to the proleptic Gregorian ordinal,
where January 1 of year 1 has ordinal 1. :exc:`ValueError` is raised unless ``1
- <= ordinal <= datetime.max.toordinal()``. The hour, minute, second and
+ <= ordinal <= datetime.max.toordinal()``. The hour, minute, second and
microsecond of the result are all 0, and :attr:`.tzinfo` is ``None``.
@@ -832,13 +954,13 @@ Other constructors, all class methods:
Return a new :class:`.datetime` object whose date components are equal to the
given :class:`date` object's, and whose time components
- are equal to the given :class:`.time` object's. If the *tzinfo*
+ are equal to the given :class:`.time` object's. If the *tzinfo*
argument is provided, its value is used to set the :attr:`.tzinfo` attribute
of the result, otherwise the :attr:`~.time.tzinfo` attribute of the *time* argument
is used.
For any :class:`.datetime` object *d*,
- ``d == datetime.combine(d.date(), d.time(), d.tzinfo)``. If date is a
+ ``d == datetime.combine(d.date(), d.time(), d.tzinfo)``. If date is a
:class:`.datetime` object, its time components and :attr:`.tzinfo` attributes
are ignored.
@@ -848,25 +970,46 @@ Other constructors, all class methods:
.. classmethod:: datetime.fromisoformat(date_string)
- Return a :class:`datetime` corresponding to a *date_string* in one of the
- formats emitted by :meth:`date.isoformat` and :meth:`datetime.isoformat`.
- Specifically, this function supports strings in the format(s)
- ``YYYY-MM-DD[*HH[:MM[:SS[.fff[fff]]]][+HH:MM[:SS[.ffffff]]]]``,
- where ``*`` can match any single character.
+ Return a :class:`.datetime` corresponding to a *date_string* in one of the
+ formats emitted by :meth:`date.isoformat` and :meth:`datetime.isoformat`.
+
+ Specifically, this function supports strings in the format:
+
+ .. code-block:: none
+
+ YYYY-MM-DD[*HH[:MM[:SS[.fff[fff]]]][+HH:MM[:SS[.ffffff]]]]
- .. caution::
+ where ``*`` can match any single character.
- This does not support parsing arbitrary ISO 8601 strings - it is only intended
- as the inverse operation of :meth:`datetime.isoformat`. A more full-featured
- ISO 8601 parser, ``dateutil.parser.isoparse`` is available in the third-party package
- `dateutil <https://dateutil.readthedocs.io/en/stable/parser.html#dateutil.parser.isoparse>`_.
+ .. caution::
- .. versionadded:: 3.7
+ This does *not* support parsing arbitrary ISO 8601 strings - it is only intended
+ as the inverse operation of :meth:`datetime.isoformat`. A more full-featured
+ ISO 8601 parser, ``dateutil.parser.isoparse`` is available in the third-party package
+ `dateutil <https://dateutil.readthedocs.io/en/stable/parser.html#dateutil.parser.isoparse>`__.
+ This does not support parsing arbitrary ISO 8601 strings - it is only intended
+ as the inverse operation of :meth:`datetime.isoformat`.
+ Examples::
+
+ >>> from datetime import datetime
+ >>> datetime.fromisoformat('2011-11-04')
+ datetime.datetime(2011, 11, 4, 0, 0)
+ >>> datetime.fromisoformat('2011-11-04T00:05:23')
+ datetime.datetime(2011, 11, 4, 0, 5, 23)
+ >>> datetime.fromisoformat('2011-11-04 00:05:23.283')
+ datetime.datetime(2011, 11, 4, 0, 5, 23, 283000)
+ >>> datetime.fromisoformat('2011-11-04 00:05:23.283+00:00')
+ datetime.datetime(2011, 11, 4, 0, 5, 23, 283000, tzinfo=datetime.timezone.utc)
+ >>> datetime.fromisoformat('2011-11-04T00:05:23+04:00') # doctest: +NORMALIZE_WHITESPACE
+ datetime.datetime(2011, 11, 4, 0, 5, 23,
+ tzinfo=datetime.timezone(datetime.timedelta(seconds=14400)))
+
+ .. versionadded:: 3.7
.. classmethod:: datetime.fromisocalendar(year, week, day)
- Return a :class:`datetime` corresponding to the ISO calendar date specified
+ Return a :class:`.datetime` corresponding to the ISO calendar date specified
by year, week and day. The non-date components of the datetime are populated
with their normal default values. This is the inverse of the function
:meth:`datetime.isocalendar`.
@@ -876,8 +1019,13 @@ Other constructors, all class methods:
.. classmethod:: datetime.strptime(date_string, format)
Return a :class:`.datetime` corresponding to *date_string*, parsed according to
- *format*. This is equivalent to ``datetime(*(time.strptime(date_string,
- format)[0:6]))``. :exc:`ValueError` is raised if the date_string and format
+ *format*.
+
+ This is equivalent to::
+
+ datetime(*(time.strptime(date_string, format)[0:6]))
+
+ :exc:`ValueError` is raised if the date_string and format
can't be parsed by :func:`time.strptime` or if it returns a value which isn't a
time tuple. For a complete list of formatting directives, see
:ref:`strftime-strptime-behavior`.
@@ -949,7 +1097,7 @@ Instance attributes (read-only):
.. attribute:: datetime.fold
- In ``[0, 1]``. Used to disambiguate wall times during a repeated interval. (A
+ In ``[0, 1]``. Used to disambiguate wall times during a repeated interval. (A
repeated interval occurs when clocks are rolled back at the end of daylight saving
time or when the UTC offset for the current zone is decreased for political reasons.)
The value 0 (1) represents the earlier (later) of the two moments with the same wall
@@ -974,7 +1122,7 @@ Supported operations:
(1)
datetime2 is a duration of timedelta removed from datetime1, moving forward in
- time if ``timedelta.days`` > 0, or backward if ``timedelta.days`` < 0. The
+ time if ``timedelta.days`` > 0, or backward if ``timedelta.days`` < 0. The
result has the same :attr:`~.datetime.tzinfo` attribute as the input datetime, and
datetime2 - datetime1 == timedelta after. :exc:`OverflowError` is raised if
datetime2.year would be smaller than :const:`MINYEAR` or larger than
@@ -988,16 +1136,16 @@ Supported operations:
(3)
Subtraction of a :class:`.datetime` from a :class:`.datetime` is defined only if
- both operands are naive, or if both are aware. If one is aware and the other is
+ both operands are naive, or if both are aware. If one is aware and the other is
naive, :exc:`TypeError` is raised.
If both are naive, or both are aware and have the same :attr:`~.datetime.tzinfo` attribute,
the :attr:`~.datetime.tzinfo` attributes are ignored, and the result is a :class:`timedelta`
- object *t* such that ``datetime2 + t == datetime1``. No time zone adjustments
+ object *t* such that ``datetime2 + t == datetime1``. No time zone adjustments
are done in this case.
If both are aware and have different :attr:`~.datetime.tzinfo` attributes, ``a-b`` acts
- as if *a* and *b* were first converted to naive UTC datetimes first. The
+ as if *a* and *b* were first converted to naive UTC datetimes first. The
result is ``(a.replace(tzinfo=None) - a.utcoffset()) - (b.replace(tzinfo=None)
- b.utcoffset())`` except that the implementation never overflows.
@@ -1006,34 +1154,31 @@ Supported operations:
*datetime2* in time.
If one comparand is naive and the other is aware, :exc:`TypeError`
- is raised if an order comparison is attempted. For equality
+ is raised if an order comparison is attempted. For equality
comparisons, naive instances are never equal to aware instances.
If both comparands are aware, and have the same :attr:`~.datetime.tzinfo` attribute, the
common :attr:`~.datetime.tzinfo` attribute is ignored and the base datetimes are
- compared. If both comparands are aware and have different :attr:`~.datetime.tzinfo`
+ compared. If both comparands are aware and have different :attr:`~.datetime.tzinfo`
attributes, the comparands are first adjusted by subtracting their UTC
offsets (obtained from ``self.utcoffset()``).
.. versionchanged:: 3.3
- Equality comparisons between naive and aware :class:`.datetime`
+ Equality comparisons between aware and naive :class:`.datetime`
instances don't raise :exc:`TypeError`.
.. note::
In order to stop comparison from falling back to the default scheme of comparing
object addresses, datetime comparison normally raises :exc:`TypeError` if the
- other comparand isn't also a :class:`.datetime` object. However,
+ other comparand isn't also a :class:`.datetime` object. However,
``NotImplemented`` is returned instead if the other comparand has a
- :meth:`timetuple` attribute. This hook gives other kinds of date objects a
- chance at implementing mixed-type comparison. If not, when a :class:`.datetime`
+ :meth:`timetuple` attribute. This hook gives other kinds of date objects a
+ chance at implementing mixed-type comparison. If not, when a :class:`.datetime`
object is compared to an object of a different type, :exc:`TypeError` is raised
- unless the comparison is ``==`` or ``!=``. The latter cases return
+ unless the comparison is ``==`` or ``!=``. The latter cases return
:const:`False` or :const:`True`, respectively.
-:class:`.datetime` objects can be used as dictionary keys. In Boolean contexts,
-all :class:`.datetime` objects are considered to be true.
-
Instance methods:
.. method:: datetime.date()
@@ -1044,7 +1189,7 @@ Instance methods:
.. method:: datetime.time()
Return :class:`.time` object with same hour, minute, second, microsecond and fold.
- :attr:`.tzinfo` is ``None``. See also method :meth:`timetz`.
+ :attr:`.tzinfo` is ``None``. See also method :meth:`timetz`.
.. versionchanged:: 3.6
The fold value is copied to the returned :class:`.time` object.
@@ -1053,7 +1198,7 @@ Instance methods:
.. method:: datetime.timetz()
Return :class:`.time` object with same hour, minute, second, microsecond, fold, and
- tzinfo attributes. See also method :meth:`time`.
+ tzinfo attributes. See also method :meth:`time`.
.. versionchanged:: 3.6
The fold value is copied to the returned :class:`.time` object.
@@ -1064,7 +1209,7 @@ Instance methods:
tzinfo=self.tzinfo, * fold=0)
Return a datetime with the same attributes, except for those attributes given
- new values by whichever keyword arguments are specified. Note that
+ new values by whichever keyword arguments are specified. Note that
``tzinfo=None`` can be specified to create a naive datetime from an aware
datetime with no conversion of date and time data.
@@ -1079,11 +1224,11 @@ Instance methods:
*self*, but in *tz*'s local time.
If provided, *tz* must be an instance of a :class:`tzinfo` subclass, and its
- :meth:`utcoffset` and :meth:`dst` methods must not return ``None``. If *self*
+ :meth:`utcoffset` and :meth:`dst` methods must not return ``None``. If *self*
is naive, it is presumed to represent time in the system timezone.
If called without arguments (or with ``tz=None``) the system local
- timezone is assumed for the target timezone. The ``.tzinfo`` attribute of the converted
+ timezone is assumed for the target timezone. The ``.tzinfo`` attribute of the converted
datetime instance will be set to an instance of :class:`timezone`
with the zone name and offset obtained from the OS.
@@ -1094,7 +1239,7 @@ Instance methods:
the same date and time data as ``dt - dt.utcoffset()``.
If you merely want to attach a time zone object *tz* to a datetime *dt* without
- adjustment of date and time data, use ``dt.replace(tzinfo=tz)``. If you
+ adjustment of date and time data, use ``dt.replace(tzinfo=tz)``. If you
merely want to remove the time zone object from an aware datetime *dt* without
conversion of date and time data, use ``dt.replace(tzinfo=None)``.
@@ -1148,25 +1293,31 @@ Instance methods:
.. method:: datetime.timetuple()
Return a :class:`time.struct_time` such as returned by :func:`time.localtime`.
- ``d.timetuple()`` is equivalent to ``time.struct_time((d.year, d.month, d.day,
- d.hour, d.minute, d.second, d.weekday(), yday, dst))``, where ``yday =
- d.toordinal() - date(d.year, 1, 1).toordinal() + 1`` is the day number within
- the current year starting with ``1`` for January 1st. The :attr:`tm_isdst` flag
- of the result is set according to the :meth:`dst` method: :attr:`.tzinfo` is
- ``None`` or :meth:`dst` returns ``None``, :attr:`tm_isdst` is set to ``-1``;
- else if :meth:`dst` returns a non-zero value, :attr:`tm_isdst` is set to ``1``;
- else :attr:`tm_isdst` is set to ``0``.
+
+ ``d.timetuple()`` is equivalent to::
+
+ time.struct_time((d.year, d.month, d.day,
+ d.hour, d.minute, d.second,
+ d.weekday(), yday, dst))
+
+ where ``yday = d.toordinal() - date(d.year, 1, 1).toordinal() + 1``
+ is the day number within the current year starting with ``1`` for January
+ 1st. The :attr:`tm_isdst` flag of the result is set according to the
+ :meth:`dst` method: :attr:`.tzinfo` is ``None`` or :meth:`dst` returns
+ ``None``, :attr:`tm_isdst` is set to ``-1``; else if :meth:`dst` returns a
+ non-zero value, :attr:`tm_isdst` is set to ``1``; else :attr:`tm_isdst` is
+ set to ``0``.
.. method:: datetime.utctimetuple()
If :class:`.datetime` instance *d* is naive, this is the same as
``d.timetuple()`` except that :attr:`tm_isdst` is forced to 0 regardless of what
- ``d.dst()`` returns. DST is never in effect for a UTC time.
+ ``d.dst()`` returns. DST is never in effect for a UTC time.
If *d* is aware, *d* is normalized to UTC time, by subtracting
``d.utcoffset()``, and a :class:`time.struct_time` for the
- normalized time is returned. :attr:`tm_isdst` is forced to 0. Note
+ normalized time is returned. :attr:`tm_isdst` is forced to 0. Note
that an :exc:`OverflowError` may be raised if *d*.year was
``MINYEAR`` or ``MAXYEAR`` and UTC adjustment spills over a year
boundary.
@@ -1174,18 +1325,18 @@ Instance methods:
.. method:: datetime.toordinal()
- Return the proleptic Gregorian ordinal of the date. The same as
+ Return the proleptic Gregorian ordinal of the date. The same as
``self.date().toordinal()``.
.. method:: datetime.timestamp()
Return POSIX timestamp corresponding to the :class:`.datetime`
- instance. The return value is a :class:`float` similar to that
+ instance. The return value is a :class:`float` similar to that
returned by :func:`time.time`.
Naive :class:`.datetime` instances are assumed to represent local
time and this method relies on the platform C :c:func:`mktime`
- function to perform the conversion. Since :class:`.datetime`
+ function to perform the conversion. Since :class:`.datetime`
supports wider range of values than :c:func:`mktime` on many
platforms, this method may raise :exc:`OverflowError` for times far
in the past or far in the future.
@@ -1204,7 +1355,7 @@ Instance methods:
.. note::
There is no method to obtain the POSIX timestamp directly from a
- naive :class:`.datetime` instance representing UTC time. If your
+ naive :class:`.datetime` instance representing UTC time. If your
application uses this convention and your system timezone is not
set to UTC, you can obtain the POSIX timestamp by supplying
``tzinfo=timezone.utc``::
@@ -1230,30 +1381,45 @@ Instance methods:
.. method:: datetime.isocalendar()
- Return a 3-tuple, (ISO year, ISO week number, ISO weekday). The same as
+ Return a 3-tuple, (ISO year, ISO week number, ISO weekday). The same as
``self.date().isocalendar()``.
.. method:: datetime.isoformat(sep='T', timespec='auto')
- Return a string representing the date and time in ISO 8601 format,
- YYYY-MM-DDTHH:MM:SS.ffffff or, if :attr:`microsecond` is 0,
- YYYY-MM-DDTHH:MM:SS
+ Return a string representing the date and time in ISO 8601 format:
+
+ - ``YYYY-MM-DDTHH:MM:SS.ffffff``, if :attr:`microsecond` is not 0
+ - ``YYYY-MM-DDTHH:MM:SS``, if :attr:`microsecond` is 0
If :meth:`utcoffset` does not return ``None``, a string is
appended, giving the UTC offset:
- YYYY-MM-DDTHH:MM:SS.ffffff+HH:MM[:SS[.ffffff]] or, if :attr:`microsecond`
- is 0 YYYY-MM-DDTHH:MM:SS+HH:MM[:SS[.ffffff]].
+
+ - ``YYYY-MM-DDTHH:MM:SS.ffffff+HH:MM[:SS[.ffffff]]``, if :attr:`microsecond`
+ is not 0
+ - ``YYYY-MM-DDTHH:MM:SS+HH:MM[:SS[.ffffff]]``, if :attr:`microsecond` is 0
+
+ Examples::
+
+ >>> from datetime import datetime, timezone
+ >>> datetime(2019, 5, 18, 15, 17, 8, 132263).isoformat()
+ '2019-05-18T15:17:08.132263'
+ >>> datetime(2019, 5, 18, 15, 17, tzinfo=timezone.utc).isoformat()
+ '2019-05-18T15:17:00+00:00'
The optional argument *sep* (default ``'T'``) is a one-character separator,
- placed between the date and time portions of the result. For example,
+ placed between the date and time portions of the result. For example::
>>> from datetime import tzinfo, timedelta, datetime
>>> class TZ(tzinfo):
- ... def utcoffset(self, dt): return timedelta(minutes=-399)
+ ... """A time zone with an arbitrary, constant -06:39 offset."""
+ ... def utcoffset(self, dt):
+ ... return timedelta(hours=-6, minutes=-39)
...
>>> datetime(2002, 12, 25, tzinfo=TZ()).isoformat(' ')
'2002-12-25 00:00:00-06:39'
+ >>> datetime(2009, 11, 27, microsecond=100, tzinfo=TZ()).isoformat()
+ '2009-11-27T00:00:00.000100-06:39'
The optional argument *timespec* specifies the number of additional
components of the time to include (the default is ``'auto'``).
@@ -1261,19 +1427,19 @@ Instance methods:
- ``'auto'``: Same as ``'seconds'`` if :attr:`microsecond` is 0,
same as ``'microseconds'`` otherwise.
- - ``'hours'``: Include the :attr:`hour` in the two-digit HH format.
- - ``'minutes'``: Include :attr:`hour` and :attr:`minute` in HH:MM format.
+ - ``'hours'``: Include the :attr:`hour` in the two-digit ``HH`` format.
+ - ``'minutes'``: Include :attr:`hour` and :attr:`minute` in ``HH:MM`` format.
- ``'seconds'``: Include :attr:`hour`, :attr:`minute`, and :attr:`second`
- in HH:MM:SS format.
+ in ``HH:MM:SS`` format.
- ``'milliseconds'``: Include full time, but truncate fractional second
- part to milliseconds. HH:MM:SS.sss format.
- - ``'microseconds'``: Include full time in HH:MM:SS.ffffff format.
+ part to milliseconds. ``HH:MM:SS.sss`` format.
+ - ``'microseconds'``: Include full time in ``HH:MM:SS.ffffff`` format.
.. note::
Excluded time components are truncated, not rounded.
- :exc:`ValueError` will be raised on an invalid *timespec* argument.
+ :exc:`ValueError` will be raised on an invalid *timespec* argument::
>>> from datetime import datetime
@@ -1295,48 +1461,64 @@ Instance methods:
.. method:: datetime.ctime()
- Return a string representing the date and time, for example ``datetime(2002, 12,
- 4, 20, 30, 40).ctime() == 'Wed Dec 4 20:30:40 2002'``. ``d.ctime()`` is
- equivalent to ``time.ctime(time.mktime(d.timetuple()))`` on platforms where the
- native C :c:func:`ctime` function (which :func:`time.ctime` invokes, but which
- :meth:`datetime.ctime` does not invoke) conforms to the C standard.
+ Return a string representing the date and time::
+
+ >>> from datetime import datetime
+ >>> datetime(2002, 12, 4, 20, 30, 40).ctime()
+ 'Wed Dec 4 20:30:40 2002'
+
+ The output string will *not* include time zone information, regardless
+ of whether the input is aware or naive.
+ ``d.ctime()`` is equivalent to::
+
+ time.ctime(time.mktime(d.timetuple()))
+
+ on platforms where the native C :c:func:`ctime` function
+ (which :func:`time.ctime` invokes, but which
+ :meth:`datetime.ctime` does not invoke) conforms to the C standard.
.. method:: datetime.strftime(format)
Return a string representing the date and time, controlled by an explicit format
- string. For a complete list of formatting directives, see
+ string. For a complete list of formatting directives, see
:ref:`strftime-strptime-behavior`.
.. method:: datetime.__format__(format)
- Same as :meth:`.datetime.strftime`. This makes it possible to specify a format
+ Same as :meth:`.datetime.strftime`. This makes it possible to specify a format
string for a :class:`.datetime` object in :ref:`formatted string
- literals <f-strings>` and when using :meth:`str.format`. For a
+ literals <f-strings>` and when using :meth:`str.format`. For a
complete list of formatting directives, see
:ref:`strftime-strptime-behavior`.
+Examples of Usage: :class:`.datetime`
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-Examples of working with datetime objects:
+Examples of working with :class:`~datetime.datetime` objects:
.. doctest::
>>> from datetime import datetime, date, time
+
>>> # Using datetime.combine()
>>> d = date(2005, 7, 14)
>>> t = time(12, 30)
>>> datetime.combine(d, t)
datetime.datetime(2005, 7, 14, 12, 30)
+
>>> # Using datetime.now() or datetime.utcnow()
>>> datetime.now() # doctest: +SKIP
datetime.datetime(2007, 12, 6, 16, 29, 43, 79043) # GMT +1
>>> datetime.utcnow() # doctest: +SKIP
datetime.datetime(2007, 12, 6, 15, 29, 43, 79060)
+
>>> # Using datetime.strptime()
>>> dt = datetime.strptime("21/11/06 16:30", "%d/%m/%y %H:%M")
>>> dt
datetime.datetime(2006, 11, 21, 16, 30)
+
>>> # Using datetime.timetuple() to get tuple of all attributes
>>> tt = dt.timetuple()
>>> for it in tt: # doctest: +SKIP
@@ -1351,6 +1533,7 @@ Examples of working with datetime objects:
1 # weekday (0 = Monday)
325 # number of days since 1st January
-1 # dst - method tzinfo.dst() returned None
+
>>> # Date in ISO format
>>> ic = dt.isocalendar()
>>> for it in ic: # doctest: +SKIP
@@ -1359,89 +1542,95 @@ Examples of working with datetime objects:
2006 # ISO year
47 # ISO week
2 # ISO weekday
- >>> # Formatting datetime
+
+ >>> # Formatting a datetime
>>> dt.strftime("%A, %d. %B %Y %I:%M%p")
'Tuesday, 21. November 2006 04:30PM'
>>> 'The {1} is {0:%d}, the {2} is {0:%B}, the {3} is {0:%I:%M%p}.'.format(dt, "day", "month", "time")
'The day is 21, the month is November, the time is 04:30PM.'
-Using datetime with tzinfo:
-
- >>> from datetime import timedelta, datetime, tzinfo, timezone
- >>> class KabulTz(tzinfo):
- ... # Kabul used +4 until 1945, when they moved to +4:30
- ... UTC_MOVE_DATE = datetime(1944, 12, 31, 20, tzinfo=timezone.utc)
- ... def utcoffset(self, dt):
- ... if dt.year < 1945:
- ... return timedelta(hours=4)
- ... elif (1945, 1, 1, 0, 0) <= dt.timetuple()[:5] < (1945, 1, 1, 0, 30):
- ... # If dt falls in the imaginary range, use fold to decide how
- ... # to resolve. See PEP495
- ... return timedelta(hours=4, minutes=(30 if dt.fold else 0))
- ... else:
- ... return timedelta(hours=4, minutes=30)
- ...
- ... def fromutc(self, dt):
- ... # A custom implementation is required for fromutc as
- ... # the input to this function is a datetime with utc values
- ... # but with a tzinfo set to self
- ... # See datetime.astimezone or fromtimestamp
- ...
- ... # Follow same validations as in datetime.tzinfo
- ... if not isinstance(dt, datetime):
- ... raise TypeError("fromutc() requires a datetime argument")
- ... if dt.tzinfo is not self:
- ... raise ValueError("dt.tzinfo is not self")
- ...
- ... if dt.replace(tzinfo=timezone.utc) >= self.UTC_MOVE_DATE:
- ... return dt + timedelta(hours=4, minutes=30)
- ... else:
- ... return dt + timedelta(hours=4)
- ...
- ... def dst(self, dt):
- ... return timedelta(0)
- ...
- ... def tzname(self, dt):
- ... if dt >= self.UTC_MOVE_DATE:
- ... return "+04:30"
- ... else:
- ... return "+04"
- ...
- ... def __repr__(self):
- ... return f"{self.__class__.__name__}()"
- ...
- >>> tz1 = KabulTz()
- >>> # Datetime before the change
- >>> dt1 = datetime(1900, 11, 21, 16, 30, tzinfo=tz1)
- >>> print(dt1.utcoffset())
- 4:00:00
- >>> # Datetime after the change
- >>> dt2 = datetime(2006, 6, 14, 13, 0, tzinfo=tz1)
- >>> print(dt2.utcoffset())
- 4:30:00
- >>> # Convert datetime to another time zone
- >>> dt3 = dt2.astimezone(timezone.utc)
- >>> dt3
- datetime.datetime(2006, 6, 14, 8, 30, tzinfo=datetime.timezone.utc)
- >>> dt2
- datetime.datetime(2006, 6, 14, 13, 0, tzinfo=KabulTz())
- >>> dt2.utctimetuple() == dt3.utctimetuple()
- True
-
-
+The example below defines a :class:`tzinfo` subclass capturing time zone
+information for Kabul, Afghanistan, which used +4 UTC until 1945
+and then +4:30 UTC thereafter::
+
+ from datetime import timedelta, datetime, tzinfo, timezone
+
+ class KabulTz(tzinfo):
+ # Kabul used +4 until 1945, when they moved to +4:30
+ UTC_MOVE_DATE = datetime(1944, 12, 31, 20, tzinfo=timezone.utc)
+
+ def utcoffset(self, dt):
+ if dt.year < 1945:
+ return timedelta(hours=4)
+ elif (1945, 1, 1, 0, 0) <= dt.timetuple()[:5] < (1945, 1, 1, 0, 30):
+ # An ambiguous ("imaginary") half-hour range representing
+ # a 'fold' in time due to the shift from +4 to +4:30.
+ # If dt falls in the imaginary range, use fold to decide how
+ # to resolve. See PEP495.
+ return timedelta(hours=4, minutes=(30 if dt.fold else 0))
+ else:
+ return timedelta(hours=4, minutes=30)
+
+ def fromutc(self, dt):
+ # Follow same validations as in datetime.tzinfo
+ if not isinstance(dt, datetime):
+ raise TypeError("fromutc() requires a datetime argument")
+ if dt.tzinfo is not self:
+ raise ValueError("dt.tzinfo is not self")
+
+ # A custom implementation is required for fromutc as
+ # the input to this function is a datetime with utc values
+ # but with a tzinfo set to self.
+ # See datetime.astimezone or fromtimestamp.
+ if dt.replace(tzinfo=timezone.utc) >= self.UTC_MOVE_DATE:
+ return dt + timedelta(hours=4, minutes=30)
+ else:
+ return dt + timedelta(hours=4)
+
+ def dst(self, dt):
+ # Kabul does not observe daylight saving time.
+ return timedelta(0)
+
+ def tzname(self, dt):
+ if dt >= self.UTC_MOVE_DATE:
+ return "+04:30"
+ return "+04"
+
+Usage of ``KabulTz`` from above::
+
+ >>> tz1 = KabulTz()
+
+ >>> # Datetime before the change
+ >>> dt1 = datetime(1900, 11, 21, 16, 30, tzinfo=tz1)
+ >>> print(dt1.utcoffset())
+ 4:00:00
+
+ >>> # Datetime after the change
+ >>> dt2 = datetime(2006, 6, 14, 13, 0, tzinfo=tz1)
+ >>> print(dt2.utcoffset())
+ 4:30:00
+
+ >>> # Convert datetime to another time zone
+ >>> dt3 = dt2.astimezone(timezone.utc)
+ >>> dt3
+ datetime.datetime(2006, 6, 14, 8, 30, tzinfo=datetime.timezone.utc)
+ >>> dt2
+ datetime.datetime(2006, 6, 14, 13, 0, tzinfo=KabulTz())
+ >>> dt2.utctimetuple() == dt3.utctimetuple()
+ True
.. _datetime-time:
:class:`.time` Objects
----------------------
-A time object represents a (local) time of day, independent of any particular
+A :class:`time` object represents a (local) time of day, independent of any particular
day, and subject to adjustment via a :class:`tzinfo` object.
.. class:: time(hour=0, minute=0, second=0, microsecond=0, tzinfo=None, *, fold=0)
- All arguments are optional. *tzinfo* may be ``None``, or an instance of a
- :class:`tzinfo` subclass. The remaining arguments must be integers in the
+ All arguments are optional. *tzinfo* may be ``None``, or an instance of a
+ :class:`tzinfo` subclass. The remaining arguments must be integers in the
following ranges:
* ``0 <= hour < 24``,
@@ -1450,7 +1639,7 @@ day, and subject to adjustment via a :class:`tzinfo` object.
* ``0 <= microsecond < 1000000``,
* ``fold in [0, 1]``.
- If an argument outside those ranges is given, :exc:`ValueError` is raised. All
+ If an argument outside those ranges is given, :exc:`ValueError` is raised. All
default to ``0`` except *tzinfo*, which defaults to :const:`None`.
Class attributes:
@@ -1503,7 +1692,7 @@ Instance attributes (read-only):
.. attribute:: time.fold
- In ``[0, 1]``. Used to disambiguate wall times during a repeated interval. (A
+ In ``[0, 1]``. Used to disambiguate wall times during a repeated interval. (A
repeated interval occurs when clocks are rolled back at the end of daylight saving
time or when the UTC offset for the current zone is decreased for political reasons.)
The value 0 (1) represents the earlier (later) of the two moments with the same wall
@@ -1511,38 +1700,32 @@ Instance attributes (read-only):
.. versionadded:: 3.6
+:class:`.time` objects support comparison of :class:`.time` to :class:`.time`,
+where *a* is considered less
+than *b* when *a* precedes *b* in time. If one comparand is naive and the other
+is aware, :exc:`TypeError` is raised if an order comparison is attempted. For equality
+comparisons, naive instances are never equal to aware instances.
-Supported operations:
-
-* comparison of :class:`.time` to :class:`.time`, where *a* is considered less
- than *b* when *a* precedes *b* in time. If one comparand is naive and the other
- is aware, :exc:`TypeError` is raised if an order comparison is attempted. For equality
- comparisons, naive instances are never equal to aware instances.
+If both comparands are aware, and have
+the same :attr:`~time.tzinfo` attribute, the common :attr:`~time.tzinfo` attribute is
+ignored and the base times are compared. If both comparands are aware and
+have different :attr:`~time.tzinfo` attributes, the comparands are first adjusted by
+subtracting their UTC offsets (obtained from ``self.utcoffset()``). In order
+to stop mixed-type comparisons from falling back to the default comparison by
+object address, when a :class:`.time` object is compared to an object of a
+different type, :exc:`TypeError` is raised unless the comparison is ``==`` or
+``!=``. The latter cases return :const:`False` or :const:`True`, respectively.
- If both comparands are aware, and have
- the same :attr:`~time.tzinfo` attribute, the common :attr:`~time.tzinfo` attribute is
- ignored and the base times are compared. If both comparands are aware and
- have different :attr:`~time.tzinfo` attributes, the comparands are first adjusted by
- subtracting their UTC offsets (obtained from ``self.utcoffset()``). In order
- to stop mixed-type comparisons from falling back to the default comparison by
- object address, when a :class:`.time` object is compared to an object of a
- different type, :exc:`TypeError` is raised unless the comparison is ``==`` or
- ``!=``. The latter cases return :const:`False` or :const:`True`, respectively.
+.. versionchanged:: 3.3
+ Equality comparisons between aware and naive :class:`~datetime.time` instances
+ don't raise :exc:`TypeError`.
- .. versionchanged:: 3.3
- Equality comparisons between naive and aware :class:`~datetime.time` instances
- don't raise :exc:`TypeError`.
-
-* hash, use as dict key
-
-* efficient pickling
-
-In boolean contexts, a :class:`.time` object is always considered to be true.
+In Boolean contexts, a :class:`.time` object is always considered to be true.
.. versionchanged:: 3.5
Before Python 3.5, a :class:`.time` object was considered to be false if it
- represented midnight in UTC. This behavior was considered obscure and
- error-prone and has been removed in Python 3.5. See :issue:`13936` for full
+ represented midnight in UTC. This behavior was considered obscure and
+ error-prone and has been removed in Python 3.5. See :issue:`13936` for full
details.
@@ -1550,16 +1733,30 @@ Other constructor:
.. classmethod:: time.fromisoformat(time_string)
- Return a :class:`time` corresponding to a *time_string* in one of the
- formats emitted by :meth:`time.isoformat`. Specifically, this function supports
- strings in the format(s) ``HH[:MM[:SS[.fff[fff]]]][+HH:MM[:SS[.ffffff]]]``.
+ Return a :class:`.time` corresponding to a *time_string* in one of the
+ formats emitted by :meth:`time.isoformat`. Specifically, this function supports
+ strings in the format:
+
+ .. code-block:: none
+
+ HH[:MM[:SS[.fff[fff]]]][+HH:MM[:SS[.ffffff]]]
+
+ .. caution::
- .. caution::
+ This does *not* support parsing arbitrary ISO 8601 strings. It is only
+ intended as the inverse operation of :meth:`time.isoformat`.
- This does not support parsing arbitrary ISO 8601 strings - it is only intended
- as the inverse operation of :meth:`time.isoformat`.
+ Examples::
- .. versionadded:: 3.7
+ >>> from datetime import time
+ >>> time.fromisoformat('04:23:01')
+ datetime.time(4, 23, 1)
+ >>> time.fromisoformat('04:23:01.000384')
+ datetime.time(4, 23, 1, 384)
+ >>> time.fromisoformat('04:23:01+04:00')
+ datetime.time(4, 23, 1, tzinfo=datetime.timezone(datetime.timedelta(seconds=14400)))
+
+ .. versionadded:: 3.7
Instance methods:
@@ -1568,7 +1765,7 @@ Instance methods:
microsecond=self.microsecond, tzinfo=self.tzinfo, * fold=0)
Return a :class:`.time` with the same value, except for those attributes given
- new values by whichever keyword arguments are specified. Note that
+ new values by whichever keyword arguments are specified. Note that
``tzinfo=None`` can be specified to create a naive :class:`.time` from an
aware :class:`.time`, without conversion of the time data.
@@ -1578,10 +1775,12 @@ Instance methods:
.. method:: time.isoformat(timespec='auto')
- Return a string representing the time in ISO 8601 format, HH:MM:SS.ffffff or, if
- :attr:`microsecond` is 0, HH:MM:SS If :meth:`utcoffset` does not return ``None``, a
- string is appended, giving the UTC offset: HH:MM:SS.ffffff+HH:MM[:SS[.ffffff]]
- or, if self.microsecond is 0, HH:MM:SS+HH:MM[:SS[.ffffff]].
+ Return a string representing the time in ISO 8601 format, one of:
+
+ - ``HH:MM:SS.ffffff``, if :attr:`microsecond` is not 0
+ - ``HH:MM:SS``, if :attr:`microsecond` is 0
+ - ``HH:MM:SS.ffffff+HH:MM[:SS[.ffffff]]``, if :meth:`utcoffset` does not return ``None``
+ - ``HH:MM:SS+HH:MM[:SS[.ffffff]]``, if :attr:`microsecond` is 0 and :meth:`utcoffset` does not return ``None``
The optional argument *timespec* specifies the number of additional
components of the time to include (the default is ``'auto'``).
@@ -1589,13 +1788,13 @@ Instance methods:
- ``'auto'``: Same as ``'seconds'`` if :attr:`microsecond` is 0,
same as ``'microseconds'`` otherwise.
- - ``'hours'``: Include the :attr:`hour` in the two-digit HH format.
- - ``'minutes'``: Include :attr:`hour` and :attr:`minute` in HH:MM format.
+ - ``'hours'``: Include the :attr:`hour` in the two-digit ``HH`` format.
+ - ``'minutes'``: Include :attr:`hour` and :attr:`minute` in ``HH:MM`` format.
- ``'seconds'``: Include :attr:`hour`, :attr:`minute`, and :attr:`second`
- in HH:MM:SS format.
+ in ``HH:MM:SS`` format.
- ``'milliseconds'``: Include full time, but truncate fractional second
- part to milliseconds. HH:MM:SS.sss format.
- - ``'microseconds'``: Include full time in HH:MM:SS.ffffff format.
+ part to milliseconds. ``HH:MM:SS.sss`` format.
+ - ``'microseconds'``: Include full time in ``HH:MM:SS.ffffff`` format.
.. note::
@@ -1603,6 +1802,7 @@ Instance methods:
:exc:`ValueError` will be raised on an invalid *timespec* argument.
+ Example::
>>> from datetime import time
>>> time(hour=12, minute=34, second=56, microsecond=123456).isoformat(timespec='minutes')
@@ -1625,7 +1825,7 @@ Instance methods:
.. method:: time.strftime(format)
Return a string representing the time, controlled by an explicit format
- string. For a complete list of formatting directives, see
+ string. For a complete list of formatting directives, see
:ref:`strftime-strptime-behavior`.
@@ -1633,7 +1833,7 @@ Instance methods:
Same as :meth:`.time.strftime`. This makes it possible to specify a format string
for a :class:`.time` object in :ref:`formatted string
- literals <f-strings>` and when using :meth:`str.format`. For a
+ literals <f-strings>` and when using :meth:`str.format`. For a
complete list of formatting directives, see
:ref:`strftime-strptime-behavior`.
@@ -1663,7 +1863,10 @@ Instance methods:
``self.tzinfo.tzname(None)``, or raises an exception if the latter doesn't
return ``None`` or a string object.
-Example:
+Examples of Usage: :class:`.time`
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Examples of working with a :class:`.time` object::
>>> from datetime import time, tzinfo, timedelta
>>> class TZ1(tzinfo):
@@ -1699,12 +1902,8 @@ Example:
.. class:: tzinfo()
This is an abstract base class, meaning that this class should not be
- instantiated directly. You need to derive a concrete subclass, and (at least)
- supply implementations of the standard :class:`tzinfo` methods needed by the
- :class:`.datetime` methods you use. The :mod:`datetime` module supplies
- a simple concrete subclass of :class:`tzinfo`, :class:`timezone`, which can represent
- timezones with fixed offset from UTC such as UTC itself or North American EST and
- EDT.
+ instantiated directly. Define a subclass of :class:`tzinfo` to capture
+ information about a particular time zone.
An instance of (a concrete subclass of) :class:`tzinfo` can be passed to the
constructors for :class:`.datetime` and :class:`.time` objects. The latter objects
@@ -1712,28 +1911,35 @@ Example:
supports methods revealing offset of local time from UTC, the name of the time
zone, and DST offset, all relative to a date or time object passed to them.
+ You need to derive a concrete subclass, and (at least)
+ supply implementations of the standard :class:`tzinfo` methods needed by the
+ :class:`.datetime` methods you use. The :mod:`datetime` module provides
+ :class:`timezone`, a simple concrete subclass of :class:`tzinfo` which can
+ represent timezones with fixed offset from UTC such as UTC itself or North
+ American EST and EDT.
+
Special requirement for pickling: A :class:`tzinfo` subclass must have an
- :meth:`__init__` method that can be called with no arguments, else it can be
- pickled but possibly not unpickled again. This is a technical requirement that
+ :meth:`__init__` method that can be called with no arguments, otherwise it can be
+ pickled but possibly not unpickled again. This is a technical requirement that
may be relaxed in the future.
A concrete subclass of :class:`tzinfo` may need to implement the following
- methods. Exactly which methods are needed depends on the uses made of aware
- :mod:`datetime` objects. If in doubt, simply implement all of them.
+ methods. Exactly which methods are needed depends on the uses made of aware
+ :mod:`datetime` objects. If in doubt, simply implement all of them.
.. method:: tzinfo.utcoffset(dt)
Return offset of local time from UTC, as a :class:`timedelta` object that is
- positive east of UTC. If local time is
- west of UTC, this should be negative. Note that this is intended to be the
- total offset from UTC; for example, if a :class:`tzinfo` object represents both
- time zone and DST adjustments, :meth:`utcoffset` should return their sum. If
- the UTC offset isn't known, return ``None``. Else the value returned must be a
- :class:`timedelta` object strictly between ``-timedelta(hours=24)`` and
- ``timedelta(hours=24)`` (the magnitude of the offset must be less
- than one day). Most implementations of :meth:`utcoffset` will probably look
- like one of these two::
+ positive east of UTC. If local time is west of UTC, this should be negative.
+
+ This represents the *total* offset from UTC; for example, if a
+ :class:`tzinfo` object represents both time zone and DST adjustments,
+ :meth:`utcoffset` should return their sum. If the UTC offset isn't known,
+ return ``None``. Else the value returned must be a :class:`timedelta` object
+ strictly between ``-timedelta(hours=24)`` and ``timedelta(hours=24)``
+ (the magnitude of the offset must be less than one day). Most implementations
+ of :meth:`utcoffset` will probably look like one of these two::
return CONSTANT # fixed-offset class
return CONSTANT + self.dst(dt) # daylight-aware class
@@ -1752,12 +1958,14 @@ Example:
Return the daylight saving time (DST) adjustment, as a :class:`timedelta`
object or
- ``None`` if DST information isn't known. Return ``timedelta(0)`` if DST is not
- in effect. If DST is in effect, return the offset as a :class:`timedelta` object
+ ``None`` if DST information isn't known.
+
+ Return ``timedelta(0)`` if DST is not in effect.
+ If DST is in effect, return the offset as a :class:`timedelta` object
(see :meth:`utcoffset` for details). Note that DST offset, if applicable, has
already been added to the UTC offset returned by :meth:`utcoffset`, so there's
no need to consult :meth:`dst` unless you're interested in obtaining DST info
- separately. For example, :meth:`datetime.timetuple` calls its :attr:`~.datetime.tzinfo`
+ separately. For example, :meth:`datetime.timetuple` calls its :attr:`~.datetime.tzinfo`
attribute's :meth:`dst` method to determine how the :attr:`tm_isdst` flag
should be set, and :meth:`tzinfo.fromutc` calls :meth:`dst` to account for
DST changes when crossing time zones.
@@ -1770,9 +1978,9 @@ Example:
must return the same result for every :class:`.datetime` *dt* with ``dt.tzinfo ==
tz`` For sane :class:`tzinfo` subclasses, this expression yields the time
zone's "standard offset", which should not depend on the date or the time, but
- only on geographic location. The implementation of :meth:`datetime.astimezone`
+ only on geographic location. The implementation of :meth:`datetime.astimezone`
relies on this, but cannot detect violations; it's the programmer's
- responsibility to ensure it. If a :class:`tzinfo` subclass cannot guarantee
+ responsibility to ensure it. If a :class:`tzinfo` subclass cannot guarantee
this, it may be able to override the default implementation of
:meth:`tzinfo.fromutc` to work correctly with :meth:`astimezone` regardless.
@@ -1782,12 +1990,12 @@ Example:
# a fixed-offset class: doesn't account for DST
return timedelta(0)
- or ::
+ or::
def dst(self, dt):
# Code to set dston and dstoff to the time zone's DST
# transition times based on the input dt.year, and expressed
- # in standard local time. Then
+ # in standard local time.
if dston <= dt.replace(tzinfo=None) < dstoff:
return timedelta(hours=1)
@@ -1804,9 +2012,9 @@ Example:
Return the time zone name corresponding to the :class:`.datetime` object *dt*, as
a string. Nothing about string names is defined by the :mod:`datetime` module,
- and there's no requirement that it mean anything in particular. For example,
+ and there's no requirement that it mean anything in particular. For example,
"GMT", "UTC", "-500", "-5:00", "EDT", "US/Eastern", "America/New York" are all
- valid replies. Return ``None`` if a string name isn't known. Note that this is
+ valid replies. Return ``None`` if a string name isn't known. Note that this is
a method rather than a fixed string primarily because some :class:`tzinfo`
subclasses will wish to return different names depending on the specific value
of *dt* passed, especially if the :class:`tzinfo` class is accounting for
@@ -1816,20 +2024,20 @@ Example:
These methods are called by a :class:`.datetime` or :class:`.time` object, in
-response to their methods of the same names. A :class:`.datetime` object passes
+response to their methods of the same names. A :class:`.datetime` object passes
itself as the argument, and a :class:`.time` object passes ``None`` as the
-argument. A :class:`tzinfo` subclass's methods should therefore be prepared to
+argument. A :class:`tzinfo` subclass's methods should therefore be prepared to
accept a *dt* argument of ``None``, or of class :class:`.datetime`.
When ``None`` is passed, it's up to the class designer to decide the best
-response. For example, returning ``None`` is appropriate if the class wishes to
-say that time objects don't participate in the :class:`tzinfo` protocols. It
+response. For example, returning ``None`` is appropriate if the class wishes to
+say that time objects don't participate in the :class:`tzinfo` protocols. It
may be more useful for ``utcoffset(None)`` to return the standard UTC offset, as
there is no other convention for discovering the standard offset.
When a :class:`.datetime` object is passed in response to a :class:`.datetime`
-method, ``dt.tzinfo`` is the same object as *self*. :class:`tzinfo` methods can
-rely on this, unless user code calls :class:`tzinfo` methods directly. The
+method, ``dt.tzinfo`` is the same object as *self*. :class:`tzinfo` methods can
+rely on this, unless user code calls :class:`tzinfo` methods directly. The
intent is that the :class:`tzinfo` methods interpret *dt* as being in local
time, and not need worry about objects in other timezones.
@@ -1839,16 +2047,16 @@ There is one more :class:`tzinfo` method that a subclass may wish to override:
.. method:: tzinfo.fromutc(dt)
This is called from the default :class:`datetime.astimezone()`
- implementation. When called from that, ``dt.tzinfo`` is *self*, and *dt*'s
- date and time data are to be viewed as expressing a UTC time. The purpose
+ implementation. When called from that, ``dt.tzinfo`` is *self*, and *dt*'s
+ date and time data are to be viewed as expressing a UTC time. The purpose
of :meth:`fromutc` is to adjust the date and time data, returning an
equivalent datetime in *self*'s local time.
Most :class:`tzinfo` subclasses should be able to inherit the default
- :meth:`fromutc` implementation without problems. It's strong enough to handle
+ :meth:`fromutc` implementation without problems. It's strong enough to handle
fixed-offset time zones, and time zones accounting for both standard and
daylight time, and the latter even if the DST transition times differ in
- different years. An example of a time zone the default :meth:`fromutc`
+ different years. An example of a time zone the default :meth:`fromutc`
implementation may not handle correctly in all cases is one where the standard
offset (from UTC) depends on the specific date and time passed, which can happen
for political reasons. The default implementations of :meth:`astimezone` and
@@ -1881,7 +2089,7 @@ In the following :download:`tzinfo_examples.py
Note that there are unavoidable subtleties twice per year in a :class:`tzinfo`
subclass accounting for both standard and daylight time, at the DST transition
-points. For concreteness, consider US Eastern (UTC -0500), where EDT begins the
+points. For concreteness, consider US Eastern (UTC -0500), where EDT begins the
minute after 1:59 (EST) on the second Sunday in March, and ends the minute after
1:59 (EDT) on the first Sunday in November::
@@ -1894,9 +2102,9 @@ minute after 1:59 (EST) on the second Sunday in March, and ends the minute after
end 23:MM 0:MM 1:MM 1:MM 2:MM 3:MM
When DST starts (the "start" line), the local wall clock leaps from 1:59 to
-3:00. A wall time of the form 2:MM doesn't really make sense on that day, so
+3:00. A wall time of the form 2:MM doesn't really make sense on that day, so
``astimezone(Eastern)`` won't deliver a result with ``hour == 2`` on the day DST
-begins. For example, at the Spring forward transition of 2016, we get
+begins. For example, at the Spring forward transition of 2016, we get::
>>> from datetime import datetime, timezone
>>> from tzinfo_examples import HOUR, Eastern
@@ -1914,14 +2122,14 @@ begins. For example, at the Spring forward transition of 2016, we get
When DST ends (the "end" line), there's a potentially worse problem: there's an
hour that can't be spelled unambiguously in local wall time: the last hour of
-daylight time. In Eastern, that's times of the form 5:MM UTC on the day
-daylight time ends. The local wall clock leaps from 1:59 (daylight time) back
+daylight time. In Eastern, that's times of the form 5:MM UTC on the day
+daylight time ends. The local wall clock leaps from 1:59 (daylight time) back
to 1:00 (standard time) again. Local times of the form 1:MM are ambiguous.
:meth:`astimezone` mimics the local clock's behavior by mapping two adjacent UTC
-hours into the same local hour then. In the Eastern example, UTC times of the
+hours into the same local hour then. In the Eastern example, UTC times of the
form 5:MM and 6:MM both map to 1:MM when converted to Eastern, but earlier times
have the :attr:`~datetime.fold` attribute set to 0 and the later times have it set to 1.
-For example, at the Fall back transition of 2016, we get
+For example, at the Fall back transition of 2016, we get::
>>> u0 = datetime(2016, 11, 6, 4, tzinfo=timezone.utc)
>>> for i in range(4):
@@ -1934,7 +2142,7 @@ For example, at the Fall back transition of 2016, we get
06:00:00 UTC = 01:00:00 EST 1
07:00:00 UTC = 02:00:00 EST 0
-Note that the :class:`datetime` instances that differ only by the value of the
+Note that the :class:`.datetime` instances that differ only by the value of the
:attr:`~datetime.fold` attribute are considered equal in comparisons.
Applications that can't bear wall-time ambiguities should explicitly check the
@@ -1946,15 +2154,17 @@ only EST (fixed offset -5 hours), or only EDT (fixed offset -4 hours)).
.. seealso::
`dateutil.tz <https://dateutil.readthedocs.io/en/stable/tz.html>`_
- The standard library has :class:`timezone` class for handling arbitrary
- fixed offsets from UTC and :attr:`timezone.utc` as UTC timezone instance.
+ The :mod:`datetime` module has a basic :class:`timezone` class (for
+ handling arbitrary fixed offsets from UTC) and its :attr:`timezone.utc`
+ attribute (a UTC timezone instance).
- *dateutil.tz* library brings the *IANA timezone database* (also known as the
- Olson database) to Python and its usage is recommended.
+ *dateutil.tz* library brings the *IANA timezone database*
+ (also known as the Olson database) to Python, and its usage is
+ recommended.
`IANA timezone database <https://www.iana.org/time-zones>`_
- The Time Zone Database (often called tz, tzdata or zoneinfo) contains code and
- data that represent the history of local time for many representative
+ The Time Zone Database (often called tz, tzdata or zoneinfo) contains code
+ and data that represent the history of local time for many representative
locations around the globe. It is updated periodically to reflect changes
made by political bodies to time zone boundaries, UTC offsets, and
daylight-saving rules.
@@ -1967,20 +2177,21 @@ only EST (fixed offset -5 hours), or only EDT (fixed offset -4 hours)).
The :class:`timezone` class is a subclass of :class:`tzinfo`, each
instance of which represents a timezone defined by a fixed offset from
-UTC. Note that objects of this class cannot be used to represent
-timezone information in the locations where different offsets are used
-in different days of the year or where historical changes have been
-made to civil time.
+UTC.
+
+Objects of this class cannot be used to represent timezone information in the
+locations where different offsets are used in different days of the year or
+where historical changes have been made to civil time.
.. class:: timezone(offset, name=None)
The *offset* argument must be specified as a :class:`timedelta`
- object representing the difference between the local time and UTC. It must
+ object representing the difference between the local time and UTC. It must
be strictly between ``-timedelta(hours=24)`` and
``timedelta(hours=24)``, otherwise :exc:`ValueError` is raised.
- The *name* argument is optional. If specified it must be a string that
+ The *name* argument is optional. If specified it must be a string that
will be used as the value returned by the :meth:`datetime.tzname` method.
.. versionadded:: 3.2
@@ -1992,9 +2203,10 @@ made to civil time.
.. method:: timezone.utcoffset(dt)
Return the fixed value specified when the :class:`timezone` instance is
- constructed. The *dt* argument is ignored. The return value is a
- :class:`timedelta` instance equal to the difference between the
- local time and UTC.
+ constructed.
+
+ The *dt* argument is ignored. The return value is a :class:`timedelta`
+ instance equal to the difference between the local time and UTC.
.. versionchanged:: 3.7
The UTC offset is not restricted to a whole number of minutes.
@@ -2002,16 +2214,17 @@ made to civil time.
.. method:: timezone.tzname(dt)
Return the fixed value specified when the :class:`timezone` instance
- is constructed. If *name* is not provided in the constructor, the
- name returned by ``tzname(dt)`` is generated from the value of the
- ``offset`` as follows. If *offset* is ``timedelta(0)``, the name
- is "UTC", otherwise it is a string 'UTC±HH:MM', where ± is the sign
- of ``offset``, HH and MM are two digits of ``offset.hours`` and
- ``offset.minutes`` respectively.
+ is constructed.
+
+ If *name* is not provided in the constructor, the name returned by
+ ``tzname(dt)`` is generated from the value of the ``offset`` as follows. If
+ *offset* is ``timedelta(0)``, the name is "UTC", otherwise it is a string in
+ the format ``UTC±HH:MM``, where ± is the sign of ``offset``, HH and MM are
+ two digits of ``offset.hours`` and ``offset.minutes`` respectively.
.. versionchanged:: 3.6
- Name generated from ``offset=timedelta(0)`` is now plain 'UTC', not
- 'UTC+00:00'.
+ Name generated from ``offset=timedelta(0)`` is now plain `'UTC'`, not
+ ``'UTC+00:00'``.
.. method:: timezone.dst(dt)
@@ -2020,7 +2233,7 @@ made to civil time.
.. method:: timezone.fromutc(dt)
- Return ``dt + offset``. The *dt* argument must be an aware
+ Return ``dt + offset``. The *dt* argument must be an aware
:class:`.datetime` instance, with ``tzinfo`` set to ``self``.
Class attributes:
@@ -2040,43 +2253,33 @@ Class attributes:
:class:`date`, :class:`.datetime`, and :class:`.time` objects all support a
``strftime(format)`` method, to create a string representing the time under the
-control of an explicit format string. Broadly speaking, ``d.strftime(fmt)``
-acts like the :mod:`time` module's ``time.strftime(fmt, d.timetuple())``
-although not all objects support a :meth:`timetuple` method.
+control of an explicit format string.
Conversely, the :meth:`datetime.strptime` class method creates a
:class:`.datetime` object from a string representing a date and time and a
-corresponding format string. ``datetime.strptime(date_string, format)`` is
-equivalent to ``datetime(*(time.strptime(date_string, format)[0:6]))``, except
-when the format includes sub-second components or timezone offset information,
-which are supported in ``datetime.strptime`` but are discarded by ``time.strptime``.
-
-For :class:`.time` objects, the format codes for year, month, and day should not
-be used, as time objects have no such values. If they're used anyway, ``1900``
-is substituted for the year, and ``1`` for the month and day.
+corresponding format string.
-For :class:`date` objects, the format codes for hours, minutes, seconds, and
-microseconds should not be used, as :class:`date` objects have no such
-values. If they're used anyway, ``0`` is substituted for them.
+The table below provides a high-level comparison of :meth:`strftime`
+versus :meth:`strptime`:
-For the :meth:`datetime.strptime` class method, the default value is ``1900-01-01T00:00:00.000``:
-any components not specified in the format string will be pulled from the default value. [#]_
++----------------+--------------------------------------------------------+------------------------------------------------------------------------------+
+| | ``strftime`` | ``strptime`` |
++================+========================================================+==============================================================================+
+| Usage | Convert object to a string according to a given format | Parse a string into a :class:`.datetime` object given a corresponding format |
++----------------+--------------------------------------------------------+------------------------------------------------------------------------------+
+| Type of method | Instance method | Class method |
++----------------+--------------------------------------------------------+------------------------------------------------------------------------------+
+| Method of | :class:`date`; :class:`.datetime`; :class:`.time` | :class:`.datetime` |
++----------------+--------------------------------------------------------+------------------------------------------------------------------------------+
+| Signature | ``strftime(format)`` | ``strptime(date_string, format)`` |
++----------------+--------------------------------------------------------+------------------------------------------------------------------------------+
-The full set of format codes supported varies across platforms, because Python
-calls the platform C library's :func:`strftime` function, and platform
-variations are common. To see the full set of format codes supported on your
-platform, consult the :manpage:`strftime(3)` documentation.
-For the same reason, handling of format strings containing Unicode code points
-that can't be represented in the charset of the current locale is also
-platform-dependent. On some platforms such code points are preserved intact in
-the output, while on others ``strftime`` may raise :exc:`UnicodeError` or return
-an empty string instead.
+:meth:`strftime` and :meth:`strptime` Format Codes
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-The following is a list of all the format codes that the C standard (1989
-version) requires, and these work on all platforms with a standard C
-implementation. Note that the 1999 version of the C standard added additional
-format codes.
+The following is a list of all the format codes that the 1989 C standard
+requires, and these work on all platforms with a standard C implementation.
+-----------+--------------------------------+------------------------+-------+
| Directive | Meaning | Example | Notes |
@@ -2137,7 +2340,7 @@ format codes.
| | left. | | |
+-----------+--------------------------------+------------------------+-------+
| ``%z`` | UTC offset in the form | (empty), +0000, | \(6) |
-| | ±HHMM[SS[.ffffff]] (empty | -0400, +1030, | |
+| | ``±HHMM[SS[.ffffff]]`` (empty | -0400, +1030, | |
| | string if the object is | +063415, | |
| | naive). | -030712.345216 | |
+-----------+--------------------------------+------------------------+-------+
@@ -2179,11 +2382,7 @@ format codes.
+-----------+--------------------------------+------------------------+-------+
Several additional directives not required by the C89 standard are included for
-convenience. These parameters all correspond to ISO 8601 date values. These
-may not be available on all platforms when used with the :meth:`strftime`
-method. The ISO 8601 year and ISO 8601 week directives are not interchangeable
-with the year and week number directives above. Calling :meth:`strptime` with
-incomplete or ambiguous ISO 8601 directives will raise a :exc:`ValueError`.
+convenience. These parameters all correspond to ISO 8601 date values.
+-----------+--------------------------------+------------------------+-------+
| Directive | Meaning | Example | Notes |
@@ -2203,9 +2402,52 @@ incomplete or ambiguous ISO 8601 directives will raise a :exc:`ValueError`.
| | Jan 4. | | |
+-----------+--------------------------------+------------------------+-------+
+These may not be available on all platforms when used with the :meth:`strftime`
+method. The ISO 8601 year and ISO 8601 week directives are not interchangeable
+with the year and week number directives above. Calling :meth:`strptime` with
+incomplete or ambiguous ISO 8601 directives will raise a :exc:`ValueError`.
+
+The full set of format codes supported varies across platforms, because Python
+calls the platform C library's :func:`strftime` function, and platform
+variations are common. To see the full set of format codes supported on your
+platform, consult the :manpage:`strftime(3)` documentation.
+
.. versionadded:: 3.6
``%G``, ``%u`` and ``%V`` were added.
+Technical Detail
+^^^^^^^^^^^^^^^^
+
+Broadly speaking, ``d.strftime(fmt)`` acts like the :mod:`time` module's
+``time.strftime(fmt, d.timetuple())`` although not all objects support a
+:meth:`timetuple` method.
+
+For the :meth:`datetime.strptime` class method, the default value is
+``1900-01-01T00:00:00.000``: any components not specified in the format string
+will be pulled from the default value. [#]_
+
+Using ``datetime.strptime(date_string, format)`` is equivalent to::
+
+ datetime(*(time.strptime(date_string, format)[0:6]))
+
+except when the format includes sub-second components or timezone offset
+information, which are supported in ``datetime.strptime`` but are discarded by
+``time.strptime``.
+
+For :class:`.time` objects, the format codes for year, month, and day should not
+be used, as :class:`time` objects have no such values. If they're used anyway,
+``1900`` is substituted for the year, and ``1`` for the month and day.
+
+For :class:`date` objects, the format codes for hours, minutes, seconds, and
+microseconds should not be used, as :class:`date` objects have no such
+values. If they're used anyway, ``0`` is substituted for them.
+
+For the same reason, handling of format strings containing Unicode code points
+that can't be represented in the charset of the current locale is also
+platform-dependent. On some platforms such code points are preserved intact in
+the output, while on others ``strftime`` may raise :exc:`UnicodeError` or return
+an empty string instead.
+
Notes:
(1)
@@ -2239,7 +2481,7 @@ Notes:
(5)
When used with the :meth:`strptime` method, the ``%f`` directive
- accepts from one to six digits and zero pads on the right. ``%f`` is
+ accepts from one to six digits and zero pads on the right. ``%f`` is
an extension to the set of format characters in the C standard (but
implemented separately in datetime objects, and therefore always
available).
@@ -2252,13 +2494,13 @@ Notes:
``%z``
:meth:`utcoffset` is transformed into a string of the form
- ±HHMM[SS[.ffffff]], where HH is a 2-digit string giving the number of UTC
- offset hours, MM is a 2-digit string giving the number of UTC offset
- minutes, SS is a 2-digit string giving the number of UTC offset
- seconds and ffffff is a 6-digit string giving the number of UTC
- offset microseconds. The ffffff part is omitted when the offset is a
- whole number of seconds and both the ffffff and the SS part is omitted
- when the offset is a whole number of minutes. For example, if
+ ``±HHMM[SS[.ffffff]]``, where ``HH`` is a 2-digit string giving the number
+ of UTC offset hours, ``MM`` is a 2-digit string giving the number of UTC
+ offset minutes, SS is a 2-digit string giving the number of UTC offset
+ seconds and ``ffffff`` is a 6-digit string giving the number of UTC
+ offset microseconds. The ``ffffff`` part is omitted when the offset is a
+ whole number of seconds and both the ``ffffff`` and the ``SS`` part is
+ omitted when the offset is a whole number of minutes. For example, if
:meth:`utcoffset` returns ``timedelta(hours=-3, minutes=-30)``, ``%z`` is
replaced with the string ``'-0330'``.
@@ -2274,12 +2516,12 @@ Notes:
``%Z``
If :meth:`tzname` returns ``None``, ``%Z`` is replaced by an empty
- string. Otherwise ``%Z`` is replaced by the returned value, which must
+ string. Otherwise ``%Z`` is replaced by the returned value, which must
be a string.
.. versionchanged:: 3.2
When the ``%z`` directive is provided to the :meth:`strptime` method, an
- aware :class:`.datetime` object will be produced. The ``tzinfo`` of the
+ aware :class:`.datetime` object will be produced. The ``tzinfo`` of the
result will be set to a :class:`timezone` instance.
(7)
@@ -2301,4 +2543,15 @@ Notes:
.. rubric:: Footnotes
.. [#] If, that is, we ignore the effects of Relativity
+
+.. [#] This matches the definition of the "proleptic Gregorian" calendar in
+ Dershowitz and Reingold's book *Calendrical Calculations*,
+ where it's the base calendar for all computations. See the book for
+ algorithms for converting between proleptic Gregorian ordinals and
+ many other calendar systems.
+
+.. [#] See R. H. van Gent's `guide to the mathematics of the ISO 8601 calendar
+ <https://www.staff.science.uu.nl/~gent0113/calendar/isocalendar.htm>`_
+ for a good explanation.
+
.. [#] Passing ``datetime.strptime('Feb 29', '%b %d')`` will fail since ``1900`` is not a leap year.
diff --git a/Misc/NEWS.d/next/Documentation/2019-05-18-16-25-44.bpo-36960.xEKHXj.rst b/Misc/NEWS.d/next/Documentation/2019-05-18-16-25-44.bpo-36960.xEKHXj.rst
new file mode 100644
index 000000000000..1d4b213367e7
--- /dev/null
+++ b/Misc/NEWS.d/next/Documentation/2019-05-18-16-25-44.bpo-36960.xEKHXj.rst
@@ -0,0 +1,2 @@
+Restructured the :mod:`datetime` docs in the interest of making them more
+user-friendly and improving readability. Patch by Brad Solomon.
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