Electronic Timers
An op-amp can be used as a timer when operated as a comparator. A simple resistor-capacitor circuit is needed.
An integrated circuit timer has the same simple cicruit as the comparator, with a flip-flop on the output for a definite high or low output. Some integrated circuit timers include a binary counter that advances one count per cycle. A decoder on the output of the timer can decode days to a year or more to be selected. Bipolar and CMOS timers are available.