I know this is not going to be foolproof because an offset isn't specific to a timezone, but with location data it seems like it would be possible to make an educated guess.
Basically, I would like to be able to take an object similar to this:
['America/Montreal', 'America/New_York', ...]
moment.tz.guess() which attempts to guess the user's most likely timezone by looking at
Date#toString. It then picks the zone with the largest population. It's not perfect, but it's close enough!
moment.tz.guess() //= America/New_York (I'm in America/Montreal, but this works too)