Timezone Global Variable Type

I have quite a few Timezones that I am dealing with, thus nearly always 3 or 4 world time clocks on my main widget. They change time to time (depending on projects and where family members moves to) and I would love to have them easily switchable in global variables. Sadly the regular list element can not even deal with all values from Etc/GMT-12 to Etc/GMT12 (at least while trying it it was cutting the list elements string and could only hold about 15 of the 25 values). So it would be super nice if there would be a prefedined list you could use for this.