How to Make Sure People in Different Time Zone Report Correct Start and Stop Time

Summary:

How to make sure people in different time zone report correct start and stop time

Content (required):

When we create work schedule we don't define which time zone the schedule is for. I assume that it is for whichever time zone set in User General Preference.

But what about people who live in time zone that is different from the one set in User General Preference. If they change user Regional setup to their correct time zone will it works?

For example: Worker A works in GMT+7 and Worker B works in GMT+9 (let's say that this is the time zone set in User General Preference). Then, I create a work schedule for both workers Mon-Fri from 9AM to 6PM. If worker A used the same time zone as Worker B, and report to work at 9AM local time, in the system it will always be considered as late. How to make it correct? Do I need to use Device time setup? Or can I use Server time setup but change the Regional user setup?