I'd just pick the timezone that gives 12:00 closest to the local solar noon and leave it at that, year round. Calling that time of the day 12:00 is completely a

I'd just pick the timezone that gives 12:00 closest to the local solar noon and leave it at that, year round. Calling that time of the day 12:00 is completely arbitrary, but any other number would be equally arbitrary, and 12:00 is a long-standing convention.