A timezone that has a variable offset from UTC
The offset might change if daylight saving time comes into effect,
or at a point in history when the region decides to change their
timezone definition.
def dst |
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dt, |
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is_dst = None |
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See datetime.tzinfo.dst
The is_dst parameter may be used to remove ambiguity during DST
transitions.
>>> from pytz import timezone
>>> tz = timezone('America/St_Johns')
>>> normal = datetime(2009, 9, 1)
>>> str(tz.dst(normal))
'1:00:00'
>>> str(tz.dst(normal, is_dst=False))
'1:00:00'
>>> str(tz.dst(normal, is_dst=True))
'1:00:00'
>>> ambiguous = datetime(2009, 10, 31, 23, 30)
>>> str(tz.dst(ambiguous, is_dst=False))
'0:00:00'
>>> str(tz.dst(ambiguous, is_dst=True))
'1:00:00'
>>> try:
... tz.dst(ambiguous)
... except AmbiguousTimeError:
... print('Ambiguous')
Ambiguous
def localize |
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dt, |
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is_dst = False |
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Convert naive time to local time.
This method should be used to construct localtimes, rather
than passing a tzinfo argument to a datetime constructor.
is_dst is used to determine the correct timezone in the ambigous
period at the end of daylight saving time.
>>> from pytz import timezone
>>> fmt = '%Y-%m-%d %H:%M:%S %Z (%z)'
>>> amdam = timezone('Europe/Amsterdam')
>>> dt = datetime(2004, 10, 31, 2, 0, 0)
>>> loc_dt1 = amdam.localize(dt, is_dst=True)
>>> loc_dt2 = amdam.localize(dt, is_dst=False)
>>> loc_dt1.strftime(fmt)
'2004-10-31 02:00:00 CEST (+0200)'
>>> loc_dt2.strftime(fmt)
'2004-10-31 02:00:00 CET (+0100)'
>>> str(loc_dt2 - loc_dt1)
'1:00:00'
Use is_dst=None to raise an AmbiguousTimeError for ambiguous
times at the end of daylight saving time
>>> try:
... loc_dt1 = amdam.localize(dt, is_dst=None)
... except AmbiguousTimeError:
... print('Ambiguous')
Ambiguous
is_dst defaults to False
>>> amdam.localize(dt) == amdam.localize(dt, False)
True
is_dst is also used to determine the correct timezone in the
wallclock times jumped over at the start of daylight saving time.
>>> pacific = timezone('US/Pacific')
>>> dt = datetime(2008, 3, 9, 2, 0, 0)
>>> ploc_dt1 = pacific.localize(dt, is_dst=True)
>>> ploc_dt2 = pacific.localize(dt, is_dst=False)
>>> ploc_dt1.strftime(fmt)
'2008-03-09 02:00:00 PDT (-0700)'
>>> ploc_dt2.strftime(fmt)
'2008-03-09 02:00:00 PST (-0800)'
>>> str(ploc_dt2 - ploc_dt1)
'1:00:00'
Use is_dst=None to raise a NonExistentTimeError for these skipped
times.
>>> try:
... loc_dt1 = pacific.localize(dt, is_dst=None)
... except NonExistentTimeError:
... print('Non-existent')
Non-existent
def normalize |
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dt |
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Correct the timezone information on the given datetime
If date arithmetic crosses DST boundaries, the tzinfo
is not magically adjusted. This method normalizes the
tzinfo to the correct one.
To test, first we need to do some setup
>>> from pytz import timezone
>>> utc = timezone('UTC')
>>> eastern = timezone('US/Eastern')
>>> fmt = '%Y-%m-%d %H:%M:%S %Z (%z)'
We next create a datetime right on an end-of-DST transition point,
the instant when the wallclocks are wound back one hour.
>>> utc_dt = datetime(2002, 10, 27, 6, 0, 0, tzinfo=utc)
>>> loc_dt = utc_dt.astimezone(eastern)
>>> loc_dt.strftime(fmt)
'2002-10-27 01:00:00 EST (-0500)'
Now, if we subtract a few minutes from it, note that the timezone
information has not changed.
>>> before = loc_dt - timedelta(minutes=10)
>>> before.strftime(fmt)
'2002-10-27 00:50:00 EST (-0500)'
But we can fix that by calling the normalize method
>>> before = eastern.normalize(before)
>>> before.strftime(fmt)
'2002-10-27 01:50:00 EDT (-0400)'
The supported method of converting between timezones is to use
datetime.astimezone(). Currently, normalize() also works:
>>> th = timezone('Asia/Bangkok')
>>> am = timezone('Europe/Amsterdam')
>>> dt = th.localize(datetime(2011, 5, 7, 1, 2, 3))
>>> fmt = '%Y-%m-%d %H:%M:%S %Z (%z)'
>>> am.normalize(dt).strftime(fmt)
'2011-05-06 20:02:03 CEST (+0200)'
def tzname |
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dt, |
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is_dst = None |
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See datetime.tzinfo.tzname
The is_dst parameter may be used to remove ambiguity during DST
transitions.
>>> from pytz import timezone
>>> tz = timezone('America/St_Johns')
>>> normal = datetime(2009, 9, 1)
>>> tz.tzname(normal)
'NDT'
>>> tz.tzname(normal, is_dst=False)
'NDT'
>>> tz.tzname(normal, is_dst=True)
'NDT'
>>> ambiguous = datetime(2009, 10, 31, 23, 30)
>>> tz.tzname(ambiguous, is_dst=False)
'NST'
>>> tz.tzname(ambiguous, is_dst=True)
'NDT'
>>> try:
... tz.tzname(ambiguous)
... except AmbiguousTimeError:
... print('Ambiguous')
Ambiguous
def utcoffset |
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dt, |
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is_dst = None |
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See datetime.tzinfo.utcoffset
The is_dst parameter may be used to remove ambiguity during DST
transitions.
>>> from pytz import timezone
>>> tz = timezone('America/St_Johns')
>>> ambiguous = datetime(2009, 10, 31, 23, 30)
>>> str(tz.utcoffset(ambiguous, is_dst=False))
'-1 day, 20:30:00'
>>> str(tz.utcoffset(ambiguous, is_dst=True))
'-1 day, 21:30:00'
>>> try:
... tz.utcoffset(ambiguous)
... except AmbiguousTimeError:
... print('Ambiguous')
Ambiguous