in a german forum is yet a Thread ref. difficult changings of watch movements (mechanic, sure) for the date or dayDate.
Some movements are changing with a click exactly at midnight. Most movements use some minutes and the slowest parts needs up to 3 hours.
This is a interesting case for us, friends of the U-series. I want to know, how "good" is our U2 watch.
The result: I'm very satisfied, the result is one of the best, I mean. The date (5) sliding a little bit 20 minutes before midnight, look to my photo at exactly midnight. The final - and complete - switch to the next number (6) was few seconds before "3 minutes after midnight". At 3 after, the processing is finished. See my final pic.
Conclusion: We know it, but we have now an another reason to say, we have a very fine watch for every challenge.