Date change (it got more accurate)

[scramjet]

I know this might have been discussed in the past, but I need a clarification...it's a 2 part question....

A few weeks ago, the date on my 16600 would switch over about 7 minutes past midnight. I read on here that it is related to how the hands were positioned when the watch is assembled. No problem that the date doesn't switch right as midnight....

Then, 3 weeks go by and now the date change occurs 2 minutes past midnight. I'm curious as to why or how its switching closer to 12am?

My second question is, does it matter what position the hour and minute hands are when you change the date manually? If so, what position should they be in, and why does it matter?

Thanks in advance!

[TheMikeOfSteel]

The same thing has happened with my new SubC. When I first got it several weeks ago, the date was flipping over at about 5-6 minutes past twelve. For the past few nights it's been closer to twelve...about 1-2 minutes past midnight.

[Andad]

Daylight saving?

And no, on a modern Rolex you can change the date at any time.

[MortgageGuy]

Personally I would just go to bed a bit earlier not see the date change and all will be good

[77T]

Now you've done it! Stop peeking at the date change, you'll put your eye out kid




Seriously now - the spring tied into the date change flip could be affected by temperature, date wheel friction and other items. Over time you may note that on certain date changes - say between 1-2-3-4-5-6 you have it switching 7 min. after midnight - and between 25-26-27-28-29-39 it switches 2 min. after midnight. Try to observe if you see a recurring pattern. In other words does it predictably repeat any pattern? If so, the date wheel is likely scrubbing another component due to slight unevenness. Once you can duplicate this, it can be addressed.

[Tools]

The date change mechanism is a cam, detent, and spring that slaps the date wheel over once every 24 hours. It doesn't care if there are hands on the watch or not - it is tied to the geartrain. It is subject to friction, oiling, and wear so may vary over time.

The watchmaker takes note of when the date changes and sets the hands onto the movement, all at 12, at that time. Some get it closer than others.

As mentioned, on a Rolex you can change the date or turn the hands at any time, forward or backward.

[scramjet]

Thanks guys, that makes sense, if the wheel is a fraction of a degree off of parallelism, to say, the face or other gears right beside it, it may rub only during a certain date range, like a bicycle wheel out of true, when the distance between the date wheel and whatever it is adjacent too is rubbing. If its rubbing, the added friction causes a 5 min delay in the date change. I will keep an eye out to see a pattern.

It's true, I don't wait up for the date to change, but when I'm up late working, in the dead of night you can hear that date change "flick" a mile away!