Clocks are adjusted to accurate time in our shop or at the factory. However, any time a pendulum clock is moved, it is likely to get slightly out of regulation and run fast or slow. This is easy to correct, and the clock will remain constant once you have readjusted it in its new environment.
Most pendulum clocks have a rating nut at the bottom of the pendulum. If you turn the nut to the right (clockwise), raising the pendulum bob, the clock will run faster. Turning it to the left or lowering the pendulum bob will slow it down. Just remember “lower is slower.” Generally, one turn of the nut will affect the timekeeping by approximately one-half to one minute a day. Remember, the round pendulum bob must move down with the rating nut to affect the timekeeping. Most clocks are accurate within one to two minutes a week when carefully regulated.
Some antique French clocks have a rate adjuster in the dial just above 12 o’clock. This is adjusted by turning the point with a small key. Usually turning to the right advances the rate and to the left slows the clock. Try adjusting it in 1/2 turn increments until correct.