Are you asking how it keeps your system up to date, or are you asking how it manages to keep track of changes to all the time zones worldwide.

If you mean the former, it doesn't. It knows on what dates each timezone enters and leaves Daylight Saving Time, but an update of the DateTime-TimeZone distro is required to get the latest definitions. For example, when the definition of US's time zones changed a few years ago, you would have had to update the distro for it to handle then-future dates correctly. Take a peek at its Changes file to see what I mean.

If you mean the latter, it gets its data from the Olson database.

Update: Major rewrite to improve clarity.

In reply to Re: TimeZone - getting next timezone transition by ikegami
in thread TimeZone - getting next timezone transition by scoops

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