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pythonpython-3.xdatetimepytz
Dani
Dani

Reputation: 544

Different behaviour of datetime.astimezone on Python 3.9.5 and Python 3.9.6

On Python 3.9.6, this works as expected:

import datetime

A = datetime.datetime(2021,1,1)

A.astimezone(datetime.timezone.utc)
    >> datetime.datetime(2021, 1, 1, 0, 0, tzinfo=datetime.timezone.utc)

But on Python 3.9.5, I get:

import datetime

A = datetime.datetime(2021,1,1)

A.astimezone(datetime.timezone.utc)
    >> datetime.datetime(2020, 12, 31, 23, 0, tzinfo=datetime.timezone.utc)

Why this behaviour? I just want to add a utc aware tzone to the naive datetime by preserving the raw datetime data, as in 3.9.6.

Upvotes: 1

Views: 5964

Answers (1)

FObersteiner
FObersteiner

Reputation: 25594

I've tested on Windows, with mentioned Python versions. The time zone setting of my machine is 'Europe/Berlin', so the naive datetime datetime(2021,1,1) is one hour ahead of UTC. Therefore conversion should give 2020-12-31T23:00:00, as you can read in the docs:

If provided, tz must be an instance of a tzinfo subclass, and its utcoffset() and dst() methods must not return None. If self is naive, it is presumed to represent time in the system timezone.

output:

Python 3.9.5 (tags/v3.9.5:0a7dcbd, May  3 2021, 17:27:52) [MSC v.1928 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> from datetime import datetime, timezone
>>> A = datetime(2021,1,1)
>>> A.astimezone(timezone.utc)
datetime.datetime(2020, 12, 31, 23, 0, tzinfo=datetime.timezone.utc)

Python 3.9.6 (tags/v3.9.6:db3ff76, Jun 28 2021, 15:26:21) [MSC v.1929 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> from datetime import datetime, timezone
>>> A = datetime(2021,1,1)
>>> A.astimezone(timezone.utc)
datetime.datetime(2020, 12, 31, 23, 0, tzinfo=datetime.timezone.utc)

So as it stands, I cannot reproduce the described behavior under the condition that I run this on the same machine with the same time zone setting for both Python versions.

Upvotes: 4

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