import datetime
import os
import time
dt = datetime.datetime(2012, 3, 12, 1, 1)
isdst = 1
for tz in ('CET', 'UTC'):
    os.environ['TZ'] = tz
    tm = dt.timetuple()[:-1] + (isdst,)
    try:
        seconds = time.mktime(tm)
        print("%s: ok" % tz)
    except OverflowError:
        print("%s: error" % tz)
    localtm = time.localtime(seconds)