Is the clock fast or slow in winter?

Speed has little effect, but it will be faster in winter.

Reason:

The clock affects the speed of the pendulum, which is controlled by the metal hairspring, so the hairspring is a main factor. From the point of view of thermal expansion and cold contraction, cold will make the hairspring shorter and harder, so it will walk faster.

Usually, adjusting the speed of the watch means adjusting the length of the speed card on the hairspring. If the length is reduced, the watch will be fast, and vice versa. )