Is it safe to change the date?

The safe way to set the date at any hour

1. Pull the crown out to the time-setting position and turn the hands to about 6:30, so they point down and away from the date mechanism.
2. Push the crown in one step to the date position and set the date to yesterday.
3. Pull back out to the time position and move the hands forward past 12 until the date jumps to today. That moment is midnight, so you now know the watch is in the morning half of its day.
4. Keep going forward to the correct time (another 12 hours if it's afternoon), then sync it to the second.

Why the window exists

A date change isn't instant. For several hours around midnight, a wheel in the movement is slowly pushing the date ring forward. If you use the quick-set crown position at the same time, the two drives push against each other and can break a tooth or bend a spring. Some movements have a shorter window and some are fully protected, but 9pm to 4am covers nearly all of them.

Your watch doesn't know morning from evening. If the date jumped around noon last time you set it, the watch is 12 hours off and its danger window is really at midday. Step 3 above fixes that.