[Python-Dev] datetime module enhancements

[BJörn Lindqvist]

On 3/9/07, Guido van Rossum <guido at python.org> wrote:
> On 3/9/07, BJörn Lindqvist <bjourne at gmail.com> wrote:
> > On 3/9/07, Guido van Rossum <guido at python.org> wrote:
> > > On 3/9/07, skip at pobox.com <skip at pobox.com> wrote:
> > > > The range of datetime objects far exceeds that of the current Unix
> > > > timestamp.  Given that the range of current (32-bit) Unix timestamps is
> > > > approximately 1970 to 2038, What would the output of this be?
> > > >
> > > >     dt = datetime.datetime(3000, 1, 1, 0, 0, 0)
> > > >     print dt.totimestamp()
> > > >     dt = datetime.datetime(1900, 1, 1, 0, 0, 0)
> > > >     print dt.totimestamp()
> > >
> > > If you extend the range to 64 bits there's no problem: the first
> > > should print 32503680000, the second -2208988800.
> >
> > I think it should be a ValueError, given that the programmer is very
> > likely to further use the returned timestamp to for example insert
> > stuff in a database. Unix timestamps are not unambiguously defined for
> > any years other than 1970 to 2038 imho.
>
> But they will be. And they already are on some platforms. The database
> should raise an OverflowError if a timestamp is out of range, but it
> would be unpythonic to limit those outcomes to 32 bits.

Then I guess datetime.fromtimestamp() also should be fixed?:

>>> datetime.fromtimestamp(-1)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: timestamp out of range for platform localtime()/gmtime() function
>>> datetime.fromtimestamp(-0.5)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: microsecond must be in 0..999999
>>> datetime.fromtimestamp(9999999999)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: timestamp out of range for platform time_t

Would be nice if datetime.fromtimestamp(dt.totimestamp()) == dt worked
for all datetimes.

-- 
mvh Björn