I know that systems are using their own time zone databases at different levels.
Is there a central place where all timezeone and DST information lives, that makes it easy for programmers to write updates to their time zone data sources?
For example, do people make provisions for a time zone for each possible combination? For example, islands in Mexican territory don't follow DST, so they would each have to be different from the three mainland time zones (that should be described w/ DST date ranges).