Change datetime to Unix time stamp in Python
Incomplete answer (doesn't deal with timezones), but hopefully useful:
time.mktime(datetime_object.timetuple())** Edited based on the following comment **
In my program, user enter datetime, select timezone. ... I created a timezone list (use pytz.all_timezones) and allow user to chose one timezone from that list.
Pytz module provides the necessary conversions. E.g. if dt is your datetime object, and user selected 'US/Eastern'
import pytz, calendartz = pytz.timezone('US/Eastern')utc_dt = tz.localize(dt, is_dst=True).astimezone(pytz.utc)print calendar.timegm(utc_dt.timetuple())The argument is_dst=True is to resolve ambiguous times during the 1-hour intervals at the end of daylight savings (see here http://pytz.sourceforge.net/#problems-with-localtime).