there's also another compromise, my stove will remember the last time it had AC power but it "loses" however many minutes it was out of power. And that can be implemented purely in non-volatile RAM (some kind of non-volatile CMOS register probably) without the actual piezo timing circuit (the clock itself can run off 60 hz utility frequency timebase). Just update the nvram once a minute.
https://en.wikipedia.org/wiki/Utility_frequency#Time_error_c...
somehow it's way less frustrating to only have to adjust the clock 30 minutes or whatever. you're not gonna be standing there for five minutes holding the button, you know? even though in practice it's not that big a deal and doesn't happen that often, it's a little human nicety.
and if you don't have time to adjust the clock at that exact moment, you can just mentally correct "I was out of power for 30 minutes so it's 30 minutes slow right now" rather than having to remember "I lost power at 3pm so that's 12:00...".
