`datetime.fromtimestamp(t).astimezone()` fails for `0`<=`t`<`86400` in Windows

[LefterisJP]

Bug report

dt.datetime.fromtimestamp(t).astimezone() fails for 0<=t<86400 in Windows for at least python 3.9, 3.10, 3.11.
Works fine in Linux, Mac.

>> import datetime as dt
>> dt.datetime.fromtimestamp(0)
datetime.datetime(1970, 1, 1, 1, 0)

>> dt.datetime.fromtimestamp(86400)
datetime.datetime(1970, 1, 2, 1, 0)

>> dt.datetime.fromtimestamp(0).astimezone()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
OSError: [Errno 22] Invalid argument

>> dt.datetime.fromtimestamp(86399).astimezone()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
OSError: [Errno 22] Invalid argument

>> dt.datetime.fromtimestamp(86400).astimezone()
datetime.datetime(1970, 1, 2, 1, 0, tzinfo=datetime.timezone(datetime.timedelta(seconds=3600), 'W. Europe Standard Time'))

A screenshot also:

Your environment

• CPython versions tested on: 3.9, 3.10, 3.11
• Operating system and architecture: Windows

Additional information

This looks very very related to this issue: #73283 but now it seems to happen for astimezone.

Linked PRs

• gh-107078: fix astimezone on Windows #107176

[littlebutt]

I think the bug was introduced by _datetimemodule.c here.

cpython/Modules/_datetimemodule.c

Line 6336 in 7fc9be3

lt = local(u2);

If the t is not large enough, the local method will return -1 since it will minus an epoch time(62135683200).

[littlebutt]

The thing is that if the t you passed is so small, the internal parameter u2 will be negative. Since the method localtime_s cannot accept a negative parameter, it will throw an OSError. I just plused a max_fold_seconds to make sure the u2 is positive. I admit it is not an elegant solotion.