Comment 5 for bug 207604

Zones mentioned in zone.tab form a superset of what's currently provided by pytz in common_timezones, because no links are in common_timezones at all. I think it may be actually more correct to include zones that are links, if such zones are in zone.tab: no backlinks are there, and all zones present there are zones belonging to countries (or crown dependencies, semi-autonomous regions, etc., but they do have ISO country code).

(Different wording of the same: common_timezones should contain all zones that the function country_timezones can return. Plus GMT, US/Eastern, et.al.)