provide tzinfo attribute on cftime.datetime objects

[rabernat]

Cftime datetimes are mostly duck-compatible with standard python datetimes. However, they lack the tzinfo attribute.

import datetime
d = datetime.datetime(2000, 1, 1)
assert d.tzinfo is None

import cftime
c = cftime.datetime(2000, 1, 1)
assert c.tzinfo is None
# -> AttributeError: 'cftime._cftime.datetime' object has no attribute 'tzinfo'

This caused a bug recently in pystack: stac-utils/pystac#238. I notice it also caused an internal bug in cftime (#126), which was fixed with #127 by replacing a reference to .tzinfo with a getattr call (similar to my workaround in stac-utils/pystac#238).

Rather than patching all the downstream libraries that might want to work with cftime datetimes (which might not realize they are not regular datetimes) to avoid assuming this attribute exist, wouldn't it be easier to provide a .tzinfo attribute on cftime dates?

Thanks for considering my suggestion.

[jswhit]

What do you suggest? cftime.datetime.tzinfo = None?

[rabernat]

Yes that would be consistent with datetime.

[jswhit]

closed by PR #209

[rabernat]

Thank you so much!