Why are the UTC offsets in the 2 datetimes created in the code below different? I'm using pytz==2019.1
from datetime import datetime
import pytz
EASTERN = pytz.timezone('US/Eastern')
dt1 = datetime.now(EASTERN)
dt2 = datetime(2020, 8, 11, 15, 30, tzinfo=EASTERN)
print(f'dt1: {dt1}')
print(f'dt2: {dt2}')
results:
dt1: 2020-08-11 18:35:47.984745-04:00
dt2: 2020-08-11 15:30:00-04:56
The first one shows an UTC offset of -04:00 which is correct (for this time of year), but the 2nd one is giving an UTC offset of -04:56.
How can I declare a datetime with the 2nd method and get the UTC offset from the first method.
The issue with the shown code is that datetime.now(tz) can handle a pytz.timezone as tz argument while the default constructor datetime(y,m,d,...) cannot. In this case, you have to use the localize method of the timezone,
from datetime import datetime
import pytz
EASTERN = pytz.timezone('US/Eastern')
dt1 = datetime.now(EASTERN)
dt2 = EASTERN.localize(datetime(2020, 8, 11, 15, 30))
print(f'dt1: {dt1}')
print(f'dt2: {dt2}')
# prints
# dt1: 2020-08-12 10:07:09.738763-04:00
# dt2: 2020-08-11 15:30:00-04:00
dateutil avoids this issue, more info can be found here. That would make the code work "as it is":
from dateutil.tz import gettz
EASTERN = gettz('US/Eastern')
dt1 = datetime.now(EASTERN)
dt2 = datetime(2020, 8, 11, 15, 30, tzinfo=EASTERN)
print(f'dt1: {dt1}')
print(f'dt2: {dt2}')
# prints e.g.
# dt1: 2020-08-12 10:20:07.796811-04:00
# dt2: 2020-08-11 15:30:00-04:00
In addition pytz is likely to be deprecated with Python 3.9 as you'll have zoneinfo as part of the standard library for these kinds of jobs.