title: Python timezones - pytz.common_timezones has too many
body: <p>There are way too many overlapping timezones in pytz's common list. Has anyone pared this down? For example there are 5 or 6 duplicate Canadian timezones and 15 or so duplicate US time zones. China is 1 timezone no DST, but has 5 entries.. By duplicate I mean GMT offset and DST are exactly the same. </p>
  
  <p>Getting rid of the timezones in pytz.country_timezones['us'] gets rid of the duplicate US timezones as it only contains the America/* zones and not the base US/* zones. This doesn't work for other countries. </p>