So many things would be fucked by a TZ change that it very rarely makes sense to consider it.

You're making a calendar app? Fuck it...some folks are gonna get confused...solved by simply emailing your users and telling them to reschedule shit because there's kind of a big event going on that everyone knows about and has been planning for for years. Hell in all liklihood this is probably easily solved by simply doing a mass migration of events scheduled before the TZ change.

You're coding for nuclear weapons? Maybe consider it. But probably not.

That is to say: there are ways to solve problems without resorting to writing the most complicated bullshit code ever seen. Unless of course you work on my team - in which case you'd be right at home.