[xenadu02]

It is very annoying because a PC motherboard using a coin-cell battery to maintain the clock can often go years without changing the battery (yes I know many of them will eventually leak but it can take decades).

There's also a US-wide time signal on WWV/WWVB - WWVB having a very simple binary-coded decimal time signal at 35 bits per minute.

Alarm clocks could dispense with the battery entirely by using non-volatile storage for the settings and alarms then using the WWVB signal to set the time. Upon resumption of power it could easily configure itself with no user interaction required.

Ironically my old alarm clock from the very early 2000s supported WWVB (with a physical switch for local time zone) but it still used non-volatile RAM for the alarm so upon losing power it would come back, get the correct time within a few minutes, but completely lose all alarms. Infuriating then and now.