[Numpy-discussion] fixing up datetime

[Mark Wiebe]

On Wed, Jun 1, 2011 at 3:52 PM, Charles R Harris
<charlesr.harris at gmail.com>wrote:

>
> <snip>
> Just a quick comment, as this really needs more thought, but time is a bag
> of worms.
>

Certainly a bag of worms, I agree.


> Trying to represent some standard -- say seconds at the solar system
> barycenter to account for general relativity -- is something that I think is
> too complicated and specialized to put into numpy.
>

>
Good support for units and delta times is very useful,
>

This part works fairly well now, except for some questions like what should
datetime("2011-01-30", "D") + timedelta(1, "M") produce. Maybe "2011-02-28",
or "2011-03-02"?


> but parsing dates and times
>

I've implemented an almost-ISO 8601 date-time parser.  I had to deviate a
bit to support years outside the little 10000-year window we use. I think
supporting more formats could be handled by writing a function which takes
its date format and outputs ISO 8601 format to feed numpy.


> and handling timezones, daylight savings,
>

The only timezone to handle is "local", which it looks like standard C has a
rich enough API for this to be ok.


> leap seconds,
>

This one can be mitigated by referencing TAI or GPS time, I think. POSIX
time looks like a can of worms though.


> business days,
>

I think Enthought has some interest in a decent business day functionality.
Some feedback from people doing time series and financial modeling would
help clarify this though. This link may provide some context:

http://www.financialcalendar.com/Data/Holidays/Formats

-Mark


> etc., is probably best served by addon packages specialized to an area of
> interest. Just my $.02
>
> Chuck
>
>
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