https://bugs.python.org/issue5288 changed datetime.timezone to accept sub-minute offsets.

The C implementation allows offsets from range (23:59, 24:00) while the python implementation does not:

# C
>>> timezone(timedelta(seconds=86399))
datetime.timezone(datetime.timedelta(seconds=86399))

# Python
>>> timezone(timedelta(seconds=86399))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "cpython/Lib/datetime.py", line 2194, in __new__
    raise ValueError("offset must be a timedelta "
ValueError: offset must be a timedelta strictly between -timedelta(hours=24) and timedelta(hours=24).

This is because _maxoffset is defined as timedelta(hours=23, minutes=59)

Second issue: The (undocumented) "min" and "max" attributes (both C and python) show 23:59
even though the C implementation can get closer to 24:00.
Should this be changed to timezone(timedelta(seconds=86399, microseconds=999999))?


(Same applies to the minimums)

I agree that the C and Python behavior should be the same, and both of them should allow all offsets less than 24 hours. I'm actually quite surprised we don't have a test for this in `datetimetester.py`.

I have been thinking about this more and I think the two issues (`min` and `max` vs. the incompatibility between C and Python) should be considered two separate issues.

My reasoning is that a change of the value of `timezone.min` and `timezone.max` is not something I'd be comfortable backporting to 3.7, because it has the potential to cause failures in some test suites (for example, `datetime.now(tz=datetime.timezone.max).isoformat()` will start returning a string that does not conform to ISO 8601, which has no support for sub-minute offsets). However, differences between the C and Python implementations are a violation of at least the spirit of PEP 399 and I think it should be backported to 3.7.

New changeset 92c7e30adf5c81a54d6e5e555a6bdfaa60157a0d by Paul Ganssle (Ngalim Siregar) in branch 'master':
bpo-37642: Update acceptable offsets in timezone (GH-14878)
https://github.com/python/cpython/commit/92c7e30adf5c81a54d6e5e555a6bdfaa60157a0d

New changeset 27b38b99b3a154fa5c25cd67fe01fb4fc04604b0 by Paul Ganssle in branch '3.8':
bpo-37642: Update acceptable offsets in timezone (GH-14878) (#15227)
https://github.com/python/cpython/commit/27b38b99b3a154fa5c25cd67fe01fb4fc04604b0

New changeset ed44b84961eb0e5b97e4866c1455ac4093d27549 by Paul Ganssle in branch '3.7':
bpo-37642: Update acceptable offsets in timezone (GH-14878) (#15226)
https://github.com/python/cpython/commit/ed44b84961eb0e5b97e4866c1455ac4093d27549