Correct time for date change - SM 300 GMT

Your description is confusing. The hour hand and date are synched on this watch, so the date change is controlled by the hour hand position, not GMT hand. To change the date, you have to move the hour hand in 1 hour jumps until it passes midnight.

It has nothing to do with the GMT hand, which only moves when the watch is hacked. The important thing is when the date changes relative to the local time (the hour hand). If your hour hand is within an hour or so to midnight, I don’t see a problem. There is some slop in the date change. The one I used to won (albeit, the standard and not the edition with the “special” caseback) changed around 1 AM.

any idea on the service history? There is a known issue with the date/hour-hand wheel that causes issues. It generally manifests as the hour hand slipping, but could manifest as a date change problem.

Ignore the GMT hand for a moment.

At what time on the standard hour/minute hands does the date change?