Abstract: An accuracy adjustment apparatus for a timepiece has an accuracy adjustment data input control section including a case-mounted switch such as a crown of the timepiece. A crown state detection signal is used to determine the state of the crown. When an accuracy adjustment data input mode is indicated based on the position of the crown, an indicator of the timepiece is driven to provide a visual indication of accuracy adjustment data selectable by operation of the crown. When the proper accuracy adjustment data has been selected, the data is stored to a memory.