Are there any legal requirements concerning airline pilots and their watches? Are there any legal requirements concerning airline pilots and their watches? Do they have to be of any particular kind and are pilots required to wear one at all?
Well, a wristwatch can't be used to sneak around the requirement that IFR requires a clock mounted in the aircraft, FAR 91.205(d)(6).  A missing or inoperative clock isn't likely in a modern airliner.  As far as the FAA is concerned, a wristwatch is nothing more than jewelry.

Ages ago, a wristwatch may have helped with calculating fuel burn and range, but even then, it was a convenience rather than mandated equipment.