PURPOSE: To simplify the whole body of a clock by driving a display means by a piezoelectric motor directly engaged therewith and reducing the number of part items, a dimension, and load to be applied.

CONSTITUTION: A display means 2 playing a role as a clock 1 such as a date display, etc., is composed of a ring date disc 4 having teeth in its inside which is arranged opposed to an opening part 6 fame in a dial 8 fixed to a case 10. Internal teeth 5 which are composed of teeth 7 separated by elliptical slots 9 having parallel side parts are provided in the disc 4. A piezoelectric mortar M1 is used for a drive means 12 which is directly cooperated with the internal teeth 5 and rotatably displaced, and suspended by a support body formed in a base 3. The piezoelectric motor M1 has an angle matching means which is integrated with its rotor and stops the rotor at a prescribed angle position or more, and an electric position detection circuit which opens at a prescribed angle position. This constitution reduces the number of part items, the dimension, and load to be applied and simplifies the whole body.