akira:

It seems cleaner than utcfromtimestamp().replace().
I think utcfromtimestamp() should have note about it.

"""
Note that it returns **naive** (tz=None) datetime.  Naive datetime is
treated as localtime in most functions.
If you want to create aware datetime, use `.fromtimestamp(ts, tz=timezone.utc)` instead.
"""

And I want to add this note to docstring too, since I read docstring before
document.