Abstract: Time-keeping apparatus includes a microcomputer having a normal, relatively high power consumption mode of operation and a standby relatively low power consumption mode of operation. The AC power supply includes energy storage providing standby power for operation during power interruption. A controllable delay arrangement causes the microcomputer to operate in a cyclical mode with a relatively long duration in the standby mode of operation and a relatively short duration in the normal mode of operation. The time period of the relatively long duration, having been previously stored in memory, is utilized for incrementing the time-keeping during the relatively short duration in the normal mode until the end of the power interruption ends the cylical mode of operation.