When creating a datetime object in a specific time zone using pytz I get a different UTC offset depending on whether I use datetime.datetime() or datetime.datetime.now().
now() seems to give the correct UTC offset for the time zone, datetime() gives an offset that I don't recognise.
Why are they different? What is the significance of the offset that datetime() assigns?
Here's my code:
import datetime
import pytz
la_paz = pytz.timezone('America/La_Paz')
a = datetime.datetime.now(la_paz)
print a, a.utcoffset()
# 2011-03-22 05:30:13-04:00 -1 day, 20:00:00
# -4 hours is the correct UTC offset for La Paz
b = datetime.datetime(2011, 03, 22, 5, 30, tzinfo=la_paz)
print b, b.utcoffset()
# 2011-03-22 05:30:00-04:33 -1 day, 19:27:00
# What is the significance of -4:33?
It seems that datetime() will use the first recorded timezone for the region by default, and in many cases (like in La Paz) this is old and no longer valid.
The datetime must instead be created naive and then localised like so:
b = la_paz.localize(datetime.datetime(2011, 03, 22, 5, 30))
print b, b.utcoffset()
now() appears to do the localization automatically.