[New-bugs-announce] [issue41118] datetime object does not preserve POSIX timestamp

[Grant Petty]

New submission from Grant Petty <gwpetty at wisc.edu>:

For complete context, see https://stackoverflow.com/questions/62582386/how-do-i-get-a-naive-datetime-object-that-correctly-uses-utc-inputs-and-preserve

Short version: It does not seem correct that a datetime object produced *from* a POSIX timestamp using utcfromtimestamp should then return a different timestamp.  As a user, I would like to be able to count on the POSIX timestamp as being the one conserved property of a datetime object, regardless of whether it is naive or time zone aware.

> dt0 = dt.datetime(year=2020, month=1, day=1,hour=0,minute=0, tzinfo=pytz.utc)
> print(dt0)

2020-01-01 00:00:00+00:00

> ts0 = dt0.timestamp()
> print(ts0)

1577836800.0

> dt1 = dt.datetime.utcfromtimestamp(ts0)
> print(dt1)

2020-01-01 00:00:00

> ts1 = dt1.timestamp()
> print(ts1)

1577858400.0

----------
messages: 372387
nosy: gpetty
priority: normal
severity: normal
status: open
title: datetime object does not preserve POSIX timestamp
type: behavior
versions: Python 3.7

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue41118>
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