Patent ID: 8427907

Claim:
A clock device, comprising: an internal clock configured to keep time; and a processing unit configured to perform the steps of: acquiring time information representing present time from an external device at preset time intervals; correcting the time kept by the internal clock based on the time information; calculating an error of the time kept by the internal clock based on the present time represented by the time information; and changing a first set value of the time interval for the acquisition of the time information by the acquiring based on the calculated error, wherein the changing further includes updating the first set value of the time interval to a second set value which is m times the first set value when the error is smaller than a first threshold value, and updating the first set value of the time interval to a third set value, which is n times the first set value when the error is larger than a second threshold value, the second threshold value being larger than the first threshold value, and wherein the multiplying factors m and n are positive values satisfying conditions m>1, n<1 and m·n≠1.