These were chunky dual-in-line devices containing clock and non-volatile RAM chips, a crystal, and a lithium battery. The battery was good for about a decade, which was fine for most PCs of the ...

Automatically adjusts to Daylight Savings Time while set the DST on. Atomic Wall Clocks Battery Operated with Alarm - This digital calendar alarm day clock required 3 “AA” long life batteries ...

[RedruM69] recently ran into a system with a dead Real Time Clock (RTC) module ... and 100 or so bytes of battery backed SRAM (before the days of cheap, plentiful flash memory).