In order to counter the effects of the Earth's gravitational force on the operation of a watch movement, the timepiece includes an escapement mechanism designed to drive a finish gear-train of a watch movement which defines a reference plane, and a balance co-operating with the escapement mechanism. Particularly, the balance is mounted in a frame (28, 60), said frame pivoting about a first axis (AA, CC) relative to the reference plane, and the orientation of the frame (28, 60) relative to the first axis (AA, CC) depends on the orientation of the Earth's gravitational force.