Conversion to UTC wrong in pytz 2024.2

[aquamatthias]

Hi,

I have this test code which started to fail with the latest release of pytz:

assert utc_str(datetime(2020, 1, 1, 0, 0, 0, 0, tzinfo=pytz.timezone("GMT"))) == "2020-01-01T00:00:00Z"

and fails with this error:

E       AssertionError: assert '2019-12-31T23:42:00Z' == '2019-12-31T23:00:00Z'

The utc_str function boils down to:

def utc_str(dt: datetime) -> str:
    return dt.astimezone(timezone.utc).strftime("%Y-%m-%dT%H:%M:%SZ")

It works as expected in pytz 2024.1.
Am I doing something wrong?

Thanks for clarification!