[creichenbach]

That's still a bit risky as Arizona might just change its time zone definition on a whim. I'm an engineer on one of the big calendaring applications, and it's mind-boggling how often stuff like this happens world-wide, sometimes short-notice (a few weeks in advance). It regularly gives us headaches.

[jaggederest]

Agreed, watching the rate of changes to timezone databases will rapidly disabuse you of the notion of any constant. It's rare that a day goes by without an update to some definition somewhere, which is astounding.

[nxobject]

It might be instructive for PHBs to have a 'hasatimezonechanged.com' website counting the days since the last timezone DB change...