When not to change the date on a mechanical watch
Why the hours around midnight are dangerous for quick-set date watches, how long the window lasts, and the safe way to set the date at any time.
The danger window
On most mechanical watches the date change takes hours. From around 9pm to 4am on the watch, a wheel inside the movement is engaged with the date ring. Using the quick-set date then makes two mechanisms push against each other, which can break a tooth or bend a spring.
Some movements have a narrower window and a few are fully protected, but unless your manual says otherwise, treat 9pm to 4am as off limits.
The safe method
- Move the hands to about 6:30, pointing down and away from the date mechanism.
- Set the date to yesterday using the quick-set position.
- Move the hands forward past 12 until the date jumps to today. That is midnight.
- Continue forward to the correct time, adding 12 hours if it is afternoon.
Morning or evening?
The hands look the same at 3am and 3pm. If the date changed at noon the last time you set the watch, it is 12 hours out and its real danger window falls in the middle of your day. Setting the date with the method above always puts the watch on the right half of the day.