Regulation
The adjustment of a watch movement to improve its rate and timekeeping accuracy.
Also known as: rate regulation, regulating a watch, timing regulation
Definition
Regulation is the adjustment of a mechanical watch's rate so that it gains or loses less time against a reference. On a traditional index-regulated movement, moving the regulator changes the effective length of the balance spring: shortening it generally makes the watch run faster and lengthening it slower. Free-sprung balances are regulated differently, usually by changing balance inertia with adjustable masses. Regulation corrects rate but is distinct from broader adjustment, which seeks stable performance across positions and conditions.
Why it matters
Regulation can improve a healthy watch that consistently runs fast or slow, but it cannot cure every timing problem. Large or erratic errors may indicate magnetism, low amplitude, wear or a need for service.