How to operate with datetime and timezones

timezones.py

# -*- coding: utf-8 -*-
from pytz import timezone
from datetime import datetime, timedelta

tz1 = timezone("Asia/Yekaterinburg")
tz2 = timezone("America/New_York")

dst1 = datetime(2013, 3,  9, tzinfo=tz2)
dst2 = datetime(2013, 3, 10, tzinfo=tz2)
dst3 = datetime(2013, 3, 11, tzinfo=tz2)

dst4 = datetime(2013, 11, 2, tzinfo=tz2)
dst5 = datetime(2013, 11, 3, tzinfo=tz2)
dst6 = datetime(2013, 11, 4, tzinfo=tz2)

dst7 = datetime(2012, 3, 10, tzinfo=tz2)
dst8 = datetime(2012, 3, 11, tzinfo=tz2)
dst9 = datetime(2012, 3, 12, tzinfo=tz2)

dst10 = datetime(2012, 11, 3, tzinfo=tz2)
dst11 = datetime(2012, 11, 4, tzinfo=tz2)
dst12 = datetime(2012, 11, 5, tzinfo=tz2)

dsts = [dst1, dst2, dst3, dst4, dst5, dst6,
        dst7, dst8, dst9, dst10, dst11, dst12]

for tz in [tz1, tz2]:
    print '*' * 80
    print tz
    print

    for dst in dsts:
        for hour in range(0, 4):
            updated = tz.normalize(dst + timedelta(hours=hour))
            print updated.strftime("%d.%m.%Y-%H:%M  %z %Z")
        print

    print '*' * 80