It's fairly established that picking a capital / large city is the correct way to specify a time zone, that usually gives you what you want. The alternatives have various problems:
* Pick a country: Some counties have multiple time zones.
* Abbreviations like EST, CET: Not right in summer.
* Words like "Eastern Time": assumes the country from context.
* Offsets like UTC-5: Doesn't follow summer time.
* Click on a map: India will ban your app because one pixel in Kashmir gave Pakistan time.
I'd suggest that the correct way to specify a time zone is the name from the IANA time zone database, which uses area (currently a continent or ocean) and location, avoiding most of these problems. Thus:
* Pick a country: Some counties have multiple time zones.
* Abbreviations like EST, CET: Not right in summer.
* Words like "Eastern Time": assumes the country from context.
* Offsets like UTC-5: Doesn't follow summer time.
* Click on a map: India will ban your app because one pixel in Kashmir gave Pakistan time.