It's not clear if someone need to choose only one of 
	- geographical timezone like Europe/Paris
	- time-shift timezone like UTC+1
or both.

If he is supposed to choose only one of them, then we need to add
something to make this clear (grey out the second tab once the user made a
selection in the first, or something like that).

If he is supposed to choose both of them, it would be nice if when I choose
Europe/Paris the second tab be updated automatically to UTC+1 (instead of
UTC-05, which is the default)

Stelian.