Reminds me of Tom Scott's video on timezones [1], where he shows how what time zone a user is in can depend on things like ethnicity: apparently, when the West Bank goes on and off Daylight Savings depends on whether you're among Israelis or not (I might have the details wrong here, please correct me if so. I couldn't find much definitive information about this).
Luckily the problem OP linked to seems easier to solve.