PURPOSE: To obtain a ROM with smaller capacity, by a method wherein alarm time information or time information related to the alarm is stored in a ROM, further, the ROM is accessed successively to be read by a prescribed clock output from a clock, and then the alarm is made to sound with alarm time calculated.

CONSTITUTION: The oscillation signal from an oscillating circuit 1 is frequency- divided in a frequency dividing stage 2, and present time and a date, etc., are clocked with a counter 3. Clock contents of the counter 3 are decoded in a decoder 4, and they are indicated properly on an indicating device 5. A counter 6 assigns as address of ROM7 that stores a time data of sunrise and sunset. In this way, the address of the ROM7 is altered and assigned for every prescribed time interval over a date, and the time data of sunrise and sunset accessed are supplied to an arithmetic circuit 8. The arithmetic circuit 8 calculates the data above, and the computed time is stored in a RAM9 as alarm time. Further, the coincidence between present time clocked at the counter 3 and the time stored in the RAM9 is detected at a coincidence checking circuit 10, thereby allowing an alarm sound generating circuit 11 to be driven and an alarm to be issued from a speaker 12.