When translating DateTime fields editors often need to enter different times for other countries. Currently only one global timezone can be set up, so DateTime fields always need to be entered in the main timezone, making it an easy place for human error, if an editor wrongly enters the time in the timezone of the translation country.
I think it would help the editor experience a lot if the timezone could be set on locale basis (maybe making it an optional toggle on DateTime field creation, so it can still be turned on/off if unwanted).