Testing/comparing pytz and dateutil for timezone handling in timezone with multiple historical UTC offsets and DST (run in interactive shell)

datetime_tests.py

# http://pypi.python.org/pypi/pytz
import datetime, pytz
fmt = '%Y-%m-%d %H:%M:%S %Z%z'
hki = pytz.timezone('Europe/Helsinki')
hki
dt_n = datetime.datetime(2012, 10, 29, 10, 34, 0)
hki.utcoffset(dt_n)
td = datetime.timedelta(days=20)
dt2_n = dt - td
hki.utcoffset(dt2_n)
dt_a = dt_n.replace(tzinfo=hki)
dt_a
dt_a.strftime(fmt)
dt_a_norm = hki.normalize(dt_a)
dt_a_norm
dt_a_norm.strftime(fmt)
dt2_a = dt_a - td
dt2_a
dt2_a.strftime(fmt)
dt2_a_norm = hki.normalize(dt2_a)
dt2_a_norm
dt2_a_norm.strftime(fmt)
dt3_a = datetime.datetime(2012, 10, 29, 10, 34, 0, tzinfo=hki) 
dt3_a
dt3_a.strftime(fmt)



# http://pypi.python.org/pypi/python-dateutil
import datetime
from dateutil import tz as timezone
fmt = '%Y-%m-%d %H:%M:%S %Z%z'
hki = timezone.gettz('Europe/Helsinki')
hki
dt_n = datetime.datetime(2012, 10, 29, 10, 34, 0)
hki.utcoffset(dt_n)
td = datetime.timedelta(days=20)
dt2_n = dt - td
hki.utcoffset(dt2_n)
dt_a = dt_n.replace(tzinfo=hki)
dt_a
dt_a.strftime(fmt)
dt2_a = dt_a - td
dt2_a
dt2_a.strftime(fmt)

dt3_a = datetime.datetime(2012, 10, 29, 10, 34, 0, tzinfo=hki) 
dt3_a
dt3_a.strftime(fmt)

# This is actaully the wrong result, it should hae been compensated for summer time as pytz does (though I can envision scenarios where that would not be desirable...)
dt4_a = dt3_a - td
dt4_a
dt4_a.strftime(fmt)

pytz_test.py

import datetime as datetime_mod
import pytz
def convertTime(timestamp):
    hki = pytz.timezone('Europe/Helsinki')
    utc = pytz.UTC
    naive = datetime_mod.datetime(int(timestamp[:4]), int(timestamp[4:6]), int(timestamp[6:8]), int(timestamp[8:10]), int(timestamp[10:12]), 0, 0)
    aware = hki.localize(naive)
    utcstamp = aware.astimezone(utc)
    print "naive=%s, aware=%s, utc=%s" % (repr(naive), repr(aware), repr(utcstamp))
    return utcstamp


print convertTime("201310150930")
print convertTime("201310310930")