Can’t you just ask the client which timezone it’s in? Every browser knows, and it will be a more accurate answer: the user might be on a foreign VPN or temporarily in another TZ, but not working on that timezone.
I’d like to set a system clock timezone via geoip only, without location lookup via wifi. On my more secure systems I have location services disabled and it’d be nice to have an accurate local time automatically.
I need to be able to send a lat/long/timestamp to get tinezone.
I’ve seen timezone maps drawn, so this information does exist somewhere, but one would have to draw polygons for each timezone and do coverage checks, which seems complicated. The time zone lines zig and zag a lot.