[lxgr]

Exif (fun exercise: find out who specifies it and when it was last updated!) actually didn't even have a way of storing timestamps in UTC or with zone information until fairly recently: It was all local times without zone information.

I've seen some software work around that by combining the local date/time with an embedded GPS tag, if present, which does contain the time in UTC.

[mlhpdx]

Ironically, time zones are a hack with bad precision about the position of the sun in the sky. The GPS coordinate side steps the nonsense (can be converted to the time zone as defined in that place at that moment).