Time detecting device for alarm clock

A time detecting device comprising an hour gear wheel for indicating time, an alarm gear wheel for indicating an alarm time and a detecting device for actuating an alarm device by mechanically shifting when the phases of said hour gear wheel and said alarm gear wheel coincide, characterized by a detecting plate supported coaxially with said hour gear wheel and said alarm gear wheel and adapted to be shiftable in the axial direction, guiding parts formed on said hour gear wheel and said detecting plate respectively for pushing and turning said detecting plate as said hour gear wheel turns in the normal direction, a hole and a projection formed on said alarm gear wheel and said detecting plate respectively for detecting the time and a cam face or cam faces formed at least on either said hour gear wheel, said alarm gear wheel or said detecting plate for pushing up said detecting plate in the direction to release the engagement between said hole and said projection irrespective of direction of turning of said alarm gear wheel.