List of current timezones and the python to generate it. Useful for generating a list of possible timezones for a user to select on a device that simply needs to track time via NTP or a realtime clock.

python timezones.py > timezones.json

It simply picks a date in winter and a date in summer for each timezone available from pytz (derived from IANA data), and determines the offset from GMT. It then groups all timezones that have the same offset(s) together. It's possible that some timezones that observe daylight savings time are grouped together, but have different rules for when DST applies. For example, one one TZ, it may start on the first Sunday in March. In another TZ, it may start on the second Monday. These two will be grouped together if they have the same offset for the winter and summer dates tested (January 1 and July 1). Because of this, it's probably best to allow a user to select any TZ that doesn't use DST, and add timezones that do use DST on an as-needed basis.

It is possible to derive the DST transition rules from the pyTZ library. This could be used to provide accurate groupings.