TimeStamper() now uses TZ-aware objects

[hynek]

The default output doesn't change but manual formatting allows for TZ data now.

Fixes #703

cc @andrei-korshikov

[andrei-korshikov]

Counterexample:

>>> datetime.datetime.now().astimezone(datetime.timezone(datetime.timedelta(hours=-5))).isoformat().rsplit("+", 1)[0]
'2025-03-08T09:55:44.415778-05:00'

datetime.isoformat() states that its ISO time zone designator format is +HH:MM[:SS[.ffffff]], but right below they give us a sample with negative offset—'2009-11-27T00:00:00.000100-06:39'.

I.e. their + in +HH:MM is actually "plus or minus". Negative offsets are totally valid by ISO 8601 / RFC 3339 anyway.

[hynek]

bleh true. great, according to the docstring, the TZ is always +zz:zz so before we start imitating using strftime, just a [:-6]?

[andrei-korshikov]

My proposal: datetime.datetime.now().astimezone().replace(tzinfo=None).isoformat(),
i.e. event_dict[key] = now().replace(tzinfo=None).isoformat()

datetime.astimezone() reads: "If you merely want to remove the timezone object from an aware datetime dt without conversion of date and time data, use dt.replace(tzinfo=None)." I think it is exactly our case: we want to convert aware time object back to naive, i.e. remove tzinfo.

[hynek]

wait, this is stupid. with either approach, I'm adding and removing the timezone instead of adding it only when necessary. i.e. in stamper_fmt. behold the genius who finally read his own code: 9e0e47e

[andrei-korshikov]

Well, isoformat() uses _tzstr() which in turn uses _format_offset(), which gives us sing and possibly seconds and microseconds.

I can't imagine real worlds applications for TZ offset with seconds and its fractions (some crazy astronomy stuff??), but is valid per current standards, so just [:-6] is not enough because time zone designator has variable length.

Yes, docstrings for these functions are confusing indeed, they repeatedly use +hh:mm which really is just one possible option...

[hynek]

since we posted at almost the same time, check back my comment before. I think I solved it pretty much perfectly.

[andrei-korshikov]

Yes, I do agree. I also tested it right now and it works as intended. Thanks to both of us:D