Traveling across multiple time zones sucks. DST is a minor inconvenience. This is my travel watch that has 31 time zones, 48 cities and UTC, 4 quick-set time zones, DST on/off for each time zone, and time zone swapping (make local time main time). You get the Casio AE1200 for between $15 and $30 online. That's a disposable resin case watch with resin "crystal." I swapped mine into an SKXMod stainless steel case with sapphire crystal and put it on a decent rubber strap. So what you see in the picture is a $125 watch. Not a great loss if it gets busted or boosted on vacation or on a business trip. Not a thief or chick magnet. 10-year battery, 100 m WR. Multiple alarms, chronograph, timer, and dodads. Can endure minor fisticuffs.
About time zones:
All time zones are based on UTC or Universal Time Coordinated. GMT (Greenwich Mean Time) is numerically identical with UTC but while GMT is a time zone, UTC is a time standard that defines time zones. However, on digital watches GMT is usually displayed as UTC. Confused yet?
There are 24 basic time zones (360 degrees divided 24 = 15 degrees). One basic time zone equals 15 degrees which represents 1 hour. This does not work for flat-earthers.
There are 11 offset time zones (8 with 30 minute and 3 with 45 minute increments).
There are 4 extra time zones around the international date line. This leads to the bizarre possibility that two locations are 24 hours apart. You may want to look up
The Island of Yesterday, Today, and Tomorrow or Diomede Islands. Also check Samoa and American Samoa.