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pythondatetimetimezonepytz

Daylight time saving aware conversion of timestamps in python

Given a timestamp without time zone (e.g. 2018-03-12 09:30:00) AND the timezone EST5EDT, the goal is to parse the data returning a datetime object that is time zone AND daylight saving aware.

from datetime import datetime
import pytz

datetime(2018, 3, 8, 9, 30, tzinfo=pytz.timezone('EST5EDT')).astimezone(pytz.utc)
# returns:
# datetime.datetime(2018, 3, 8, 14, 30, tzinfo=<UTC>)

datetime(2018, 3, 12, 9, 30, tzinfo=pytz.timezone('EST5EDT')).astimezone(pytz.utc)
# returns:
# datetime.datetime(2018, 3, 12, 14, 30, tzinfo=<UTC>)
# BUT should return (second Sunday of march the daylight saving changes by 1 hour):
# datetime.datetime(2018, 3, 12, 13, 30, tzinfo=<UTC>)
Solution

  • Never set tzinfo directly when creating datetimes. Always use the localize() method of the timezone (see the note at the top of http://pytz.sourceforge.net/):

    pytz.timezone('EST5EDT').localize(
    datetime(2018, 3, 12, 9, 30)
).astimezone(pytz.utc)