[BUG] ZoneInfo does not support datetime.Time and utcoffset can't be retrieved

[07pepa]

Bug report

Bug description:

this function does not support datetime.time

cpython/Lib/zoneinfo/_zoneinfo.py

Line 187 in 558b517

(dt.toordinal() - EPOCHORDINAL) * 86400

def test():
 from zoneinfo import ZoneInfo
 from datetime import time
 t=time(12, 4, 5, 123456, tzinfo=ZoneInfo("Europe/Prague"), fold=1)
 if t.tzinfo.utcoffset(None) is None:
 # if prevuous does not work this should but fails with
 # AttributeError: 'datetime.time' object has no attribute 'toordinal'
 t.tzinfo.utcoffset(t)

i propose checking if instance is time and then skip to ordinal like so

 def _get_local_timestamp(self, dt):
 return (
 (dt.toordinal() - EPOCHORDINAL) * 86400 if not isinstance(dt, time) else 0
 + dt.hour * 3600
 + dt.minute * 60
 + dt.second
 )

this issue is blocker for pydantic/speedate#62

if this is confirmed i am open to do PR or leave it to someone else Maybe there is something more i am not seeing

CPython versions tested on:

3.12

Operating systems tested on:

macOS

[JamesParrott]

I can recreate this on Windows, but below, aren't you asking zoneinfo a question that has an ambiguous answer?

t=time(12, 4, 5, 123456, tzinfo=ZoneInfo("Europe/Prague"), fold=1)
t.tzinfo.utcoffset(t)

t.tzinfo.utcoffset(t)utcoffset expects a datetime, so that it can figure out whether or not "Europe/Prague" is on daylight savings time, at the datetime in question.

[07pepa]

actualy this works with pytz so maybe its pytz bug ?

 from pytz import timezone
 from datetime import time
 t = time(12, 4, 5, 123456, tzinfo=timezone("Europe/Prague"), fold=1)
 if t.tzinfo.utcoffset(None) is None:
 print(t.tzinfo.utcoffset(t))

[JamesParrott]

I don't think it's a bug. It's Python requiring you to explicitly specify from which date you wish the daylight savings time to be used, for a time zone's UTC offset (which may vary on different days of the year).

[07pepa]

That seems logical gona file bug on pytz

[JamesParrott]

This is outside of CPython's scope now.

But, @07pepa I don't think it's a bug in pytz either. pytz has just chosen to always return self._utcoffset from timezone.utcoffset:

 def utcoffset(self, dt, is_dst=None):
 '''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

 '''
 if dt is None:
 return None
 elif dt.tzinfo is not self:
 dt = self.localize(dt, is_dst)
 return dt.tzinfo._utcoffset
 else:
 return self._utcoffset

https://github.com/stub42/pytz/blob/fb43f957c5149e750c3be3cfc72b22ad94db4886/src/pytz/tzinfo.py#L422