Can Dates be Timezone-Aware in Python?

Question

There's lots of SO answers on ensuring datetimes are a particular timezone. For example you can ensure your datetime is UTC with

from datetime import datetime
import pytz

now_utc = datetime.utcnow()

which yields:

datetime.datetime(2017, 5, 11, 17, 37, 5, 602054)

you can make that datetime aware of its timezone (e.g. for asserting two different datetime objects are from the same timezone) with

now_utc_aware = datetime.now(pytz.utc)

datetime.datetime(2017, 5, 11, 17, 38, 2, 757587, tzinfo=< UTC>)

But when I pull the date from a timezone-aware datetime, I seem to lose the timezone-awareness.

now_utc_aware.date()

datetime.date(2017, 5, 11)

Interestingly, there's a SO question which seems to ask exactly this, and about a date specifically (datetime.today()), but the answers (including an accepted one) relate to datetimes. The code I've seen to add timezone awareness to datetimes all seem to throw errors on my datetime.date object.

Is it possible to add timezone awareness to a date object?

Why, and more importantly, how? The fundamental aspect of a timezone is the time offset. The date only plays a secondary role in changing how the time is adjusted throughout the year. If you added the awareness to just a date, what would it look like? What operations would make sense? — Stephen Rauch, May 12 '17 at 00:59
I imagine a case where you have events logged with a `datetime.today()` across different pieces of software, logging info in different tables. Someone joining tables on date might want to confirm that the `date`s all refer to the same dates, i.e. `.today()`s logged using the same timezone as opposed to disparate local timezones. — Max Power, May 12 '17 at 01:12
I agree with your question though that the notion of time-awareness is much less straightforward for dates than datetimes. Maybe it is meaningless. Hence my question of "can dates be time-aware" not "how do I make dates time-aware?" — Max Power, May 12 '17 at 01:14

score 4 · Accepted Answer · answered May 16 '17 at 20:30

From the Python docs:

class datetime.date
An idealized naive date, ... Attributes: year, month, and day.

There's nothing there for time or time zone. It's just a date.

While it is true that not everywhere on Earth is on the same date simultaneously (because of time zones), that doesn't mean a date itself has time zone awareness.

As a real-world analogy, think of a date as just a square on a calendar. One cannot start talking about timezones without introducing time, which is measured by a clock, not a calendar.

Can Dates be Timezone-Aware in Python?

1 Answers1