guess returns obsolete timezones (likely due to Intl)

[trevorgehman]

I'm running into a situation where moment.tz.guess() is returning the obsolete timezone America/Indianapolis instead of the correct America/Indiana/Indianapolis. I'm not familiar enough with the intricacies of how this library is processing the IANA data, but I just wanted to post this issue in case others are running into it.

Not sure whether it's related to this (#835) which specifically mentions the America/Indiana/Indianapolis timezone.

[trevorgehman]

I think this is actually related to this issue: #687

On the latest Mac OSX you can set your timezone and it looks like legacy timezones are sometimes used, such as America/Montreal and America/Indianapolis. Then in Safari and Chrome that is what is returned:

Intl.DateTimeFormat().resolvedOptions().timeZone
"America/Indianapolis"

I imagine that the only workaround is to check if a legacy timezone is an alias of another timezone (https://en.wikipedia.org/wiki/List_of_tz_database_time_zones#Legend) and then return the correct timezone.

[ichernev]

@trevorgehman well, there are 2 parts in this, if guess indeed uses Intl in your case, then it is "not our problem". Maybe it could make sense to add an API/option to only do the manual guessing and not rely on broken Intl implementation, that would be more configurable.

Could you modify the rebuildGuess function to not use Intl and see if the problem persists?

[Petercopter]

This is still a problem. It's definitely not Moment, because I'm using this:

Intl.DateTimeFormat().resolvedOptions().timeZone

I've got a Ruby on Rails backend that is expecting America/Indiana/Indianapolis, and gettingAmerica/Indianapolis from the browser.