A triple (Lat/Lon/UTC Date) <-> TimeZone at the very least.

Time zones are political | * social* especially in the twilight zone between two otherwise well defined zones.

If a country is mostly in TimeZone X then often an extrusion that goes well into TimeZone Y will remain with clocks aligned to TZ-X unless some local political change is made (to be more or less sensible).

See (current TimeZone Map):

https://www.timeanddate.com/time/map/

and note that cities have changed time zones (not daylight savings changes, actual changes to core time zone) in the past and will almostly certainly do so again in the future.