import datetime, pytz
date_paris = datetime.datetime(2013, 9, 3, 16, 0, tzinfo=pytz.timezone(
    'Europe/Paris'))
date_utc = datetime.datetime(2013, 9, 3, 16, 0, tzinfo=pytz.utc)
date_paris.astimezone(pytz.utc)
date_utc.astimezone(pytz.timezone('Europe/Paris'))
timezone conversion in Python