diff options
Diffstat (limited to 'Doc/library/datetime.rst')
| -rw-r--r-- | Doc/library/datetime.rst | 39 |
1 files changed, 28 insertions, 11 deletions
diff --git a/Doc/library/datetime.rst b/Doc/library/datetime.rst index 1f4cfba..a6c1997 100644 --- a/Doc/library/datetime.rst +++ b/Doc/library/datetime.rst @@ -721,6 +721,22 @@ Other constructors, all class methods: It's common for this to be restricted to years in 1970 through 2038. See also :meth:`fromtimestamp`. + On the POSIX compliant platforms, ``utcfromtimestamp(timestamp)`` + is equivalent to the following expression:: + + datetime(1970, 1, 1) + timedelta(seconds=timestamp) + + There is no method to obtain the timestamp from a :class:`datetime` + instance, but POSIX timestamp corresponding to a :class:`datetime` + instance ``dt`` can be easily calculated as follows. For a naive + ``dt``:: + + timestamp = (dt - datetime(1970, 1, 1)) / timedelta(seconds=1) + + And for an aware ``dt``:: + + timestamp = (dt - datetime(1970, 1, 1, tzinfo=timezone.utc)) / timedelta(seconds=1) + .. classmethod:: datetime.fromordinal(ordinal) @@ -1564,11 +1580,12 @@ only EST (fixed offset -5 hours), or only EDT (fixed offset -4 hours)). :class:`timezone` Objects -------------------------- -A :class:`timezone` object represents a timezone that is 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. +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. .. class:: timezone(offset[, name]) @@ -1737,8 +1754,7 @@ format codes. | | decimal number [00,99]. | | +-----------+--------------------------------+-------+ | ``%Y`` | Year with century as a decimal | \(5) | -| | number [0001,9999] (strptime), | | -| | [1000,9999] (strftime). | | +| | number [0001,9999]. | | +-----------+--------------------------------+-------+ | ``%z`` | UTC offset in the form +HHMM | \(6) | | | or -HHMM (empty string if the | | @@ -1772,10 +1788,7 @@ Notes: calculations when the day of the week and the year are specified. (5) - For technical reasons, :meth:`strftime` method does not support - dates before year 1000: ``t.strftime(format)`` will raise a - :exc:`ValueError` when ``t.year < 1000`` even if ``format`` does - not contain ``%Y`` directive. The :meth:`strptime` method can + The :meth:`strptime` method can parse years in the full [1, 9999] range, but years < 1000 must be zero-filled to 4-digit width. @@ -1783,6 +1796,10 @@ Notes: In previous versions, :meth:`strftime` method was restricted to years >= 1900. + .. versionchanged:: 3.3 + In version 3.2, :meth:`strftime` method was restricted to + years >= 1000. + (6) For example, if :meth:`utcoffset` returns ``timedelta(hours=-3, minutes=-30)``, ``%z`` is replaced with the string ``'-0330'``. |