If you remember back to the early 2000s Swatch as a marketing gimmick proposed something called 'Swatch Internet Time' which was "designed" (and I use that word in the loosest possible sense) to solve this very problem. I think a couple of Ericsson handsets had support for it.

Wikipedia has the gory details for those interesting in that bit of trivia. I've used it as a programming exercise when interviewing candidates a couple of times.