How do you convert a datetime/timestamp from one timezone to another timezone?

If you know your origin timezone and the new timezone that you want to convert it to, it turns out to be very straightforward:

1. Make two pytz.timezone objects, one for the current timezone and one for the new timezone e.g. pytz.timezone("US/Pacific"). You can find a list of all official timezones in pytz library: import pytz; pytz.all_timezones

2. Localize the datetime/timestamp of interest to the current timezone e.g.

current_timezone = pytz.timezone("US/Eastern")
localized_timestamp = current_timezone.localize(timestamp)

3. Convert to new timezone using .astimezone() on the newly localized datetime/timestamp from step 2 with the desired timezone’s pytz object as input e.g. localized_timestamp.astimezone(new_timezone).

Done!

As a full example:

import datetime
import pytz

# a timestamp I'd like to convert
my_timestamp = datetime.datetime.now()

# create both timezone objects
old_timezone = pytz.timezone("US/Eastern")
new_timezone = pytz.timezone("US/Pacific")

# two-step process
localized_timestamp = old_timezone.localize(my_timestamp)
new_timezone_timestamp = localized_timestamp.astimezone(new_timezone)

# or alternatively, as an one-liner
new_timezone_timestamp = old_timezone.localize(my_timestamp).astimezone(new_timezone) 

Bonus: but if all you need is the current time in a specific timezone, you can conveniently pass that timezone directly into datetime.now() to get the current times directly:

datetime.datetime.now(new_timezone)

When it comes to needing timezones conversions generally, I would strongly advise that one should store all timestamps in your database in UTC, which has no daylight savings time (DST) transition. And as a good practice, one should always choose to enable time zone support (even if your users are all in a single time zone!). This will help you avoid the DST transition problem that plagues so much software today.

Beyond DST, time in software can be generally quite tricky. To get a sense of just how difficult it is to deal with time in software in general, here is a potentially enlightening resource: http://yourcalendricalfallacyis.com

Even a seemingly simple operation as converting a datetime/timestamp into a date can become non-obvious. As this helpful documentation points out:

A datetime represents a point in time. It’s absolute: it doesn’t depend on anything. On the contrary, a date is a calendaring concept. It’s a period of time whose bounds depend on the time zone in which the date is considered. As you can see, these two concepts are fundamentally different.

Understanding this difference is a key step towards avoiding time-based bugs. Good luck.