Who needs radio sync signals, NTP servers, or a freaking GPS module (lol) when we have this great hardwired 60 Hz frequency reference which is measured and adjusted for long-term stability...
https://en.wikipedia.org/wiki/Utility_frequency#Long-term_st...
> Today, AC-power network operators regulate the daily average frequency so that clocks stay within a few seconds of correct time. In practice the nominal frequency is raised or lowered by a specific percentage to maintain synchronization. Over the course of a day, the average frequency is maintained at the nominal value within a few hundred parts per million.[19] In the synchronous grid of Continental Europe, the deviation between network phase time and UTC (based on International Atomic Time) is calculated at 08:00 each day in a control center in Switzerland. The target frequency is then adjusted by up to ±0.01 Hz (±0.02%) from 50 Hz as needed, to ensure a long-term frequency average of exactly 50 Hz × 60 s/min × 60 min/h × 24 h/d = 4320000 cycles per day.[20] In North America, whenever the error exceeds 10 seconds for the east, 3 seconds for Texas, or 2 seconds for the west, a correction of ±0.02 Hz (0.033%) is applied. Time error corrections start and end either on the hour or on the half-hour.[21][22] Efforts to remove the TEC in North America are described at electric clock.
The reason these clocks are so bad is that they use bad RTC units to save a couple dollars. A bad RTC can be had for pennies. A good one (like a DS3231) is $4! Thus, we are all stuck with bad clocks; AC powered or otherwise.
GPS/NTP/WWVB exist to get the time right initially. A clock will be wrong if you set it to the wrong time, even if you have a perfect frequency reference.
That might be a fun project, but I'd worry a bit about the future of RF time sync. The program was almost shut down this year but was funded after a small fight. I wouldn't be surprised if the funding doesn't come through the next round.
My dumb alarm clock is the last and only thing I possess that requires I set the time manually. And it drifts. Even my wristwatch autosynchronizes every night to the time server signal sent over RF from Denver. I've seriously considered modding the alarm clock to autosync that way as well.
My alarm clock is a sunrise alarm clock with a 100W bulb. Can't quite replace with a cell phone. But maybe with smart bulbs. Hmm, I might have to rethink this whole thing.