Update time zone when user travels
You can use javascript to get the browser timezone. Assuming their computer timezone is updated, their browser timezone will change.

var offset = new Date().getTimezoneOffset();


Or if you want the name you'll have to do something like https://stackoverflow.com/questions/2853474/can-i-get-the-browser-time-zone-in-asp-net-or-do-i-have-to-rely-on-js-operations

Sadly there is no way to do this without Javascript.