I have a similar “smart” clock-radio that auto-resets (after a power outage) to being incorrect by 23 hours. So it looks like it’s off by 1 hour, but it switches for DST one day early. I used to manually set the time on that clock, but the power in our house flickers often enough that I found it a hassle. So now I just remember that it’s off by 1 hour (sort of).
It could be worse. The first changeover after the date change, I saw that my cell phone hadn’t changed. “Huh”, I thought, “I’d have thought that would change automatically, to match the towers. Oh well, I guess I’ll just reset it manually”. So I did, and a second after I changed it, it reverted. It was automatically matching the time on the cell towers. And those had the wrong automatic-change date.
Chronos, back in the day (~2000) my cellphone said it was April 31 for most of a day. As a programmer, it amused me immensely. Times and dates are a pain to deal with!
A zillion years ago some colleagues were messing about with building a computer. Back when you could wire wrap a design. They wanted a real time clock controller. TI made one. It had a daylight savings mode. The dates were hard wired. We are in Australia. Fail. Worse, it looked as if there had been a change in the US dates since the chip was designed, and the mode would get it wrong anyway.
It took a while for computer systems and operating system support to get daylight savings time to work properly. First step was to use UTC as the base time for all operations. Then make a configurable system that applies the offset as and when needed when presenting times and dates. Which gets us the TZ system used by most Unix/Posix systems. What is quite interesting is that the TZ configuration contains the rules for all dates. For instance a file with a creation date decades ago will still display that time as the correct wall time on that date, even if the DST rules have changed since then. And for the OCD geeks, some rules go back many decades before. (Unix time is signed, so can represent dates prior to 1970. So this actually works.) If the rules change you need to update the rules. Updates usually come as part of ordinary OS updates so nobody sees it.
Before that, computers in countries east of 0 longitude would set the local clock offset to be negative relative to UTC. Or, if no offset was supported, the local clock would be set to local time. Which was bad. Most systems do not cope well with time going backwards. All manner of assumptions break. Networks of computer systems do not cope at all.
Phones are weird. Any phone with GPS knows GPS time. But they don’t directly use it. The NTP time service from the cell is more authoritative for management tasks. Cell operation is usually slaved to GPS time frequency for stability reasons. But doesn’t mirror GPS time. The cell time infrastructure should be rooted in a proper stratum 1 time server. Getting your phone the local Timezone and thus offset from UTC is a separate bit of magic that uses the Network Identity and Time Zone (NITZ) protocol, which is part of the cell operations not internet. NITZ isn’t universally supported and can be wrong. It doesn’t always update on your phone immediately, and is tied to the cell you are receiving.
Leap seconds remain a difficult problem. There is no one perfect answer to how to manage them. GPS time is currently ahead of UTC by 18 seconds because it doesn’t do leap seconds. There is a proposal to stop doing leap seconds for UTC and let the Earth drift off from alignment. IMHO this is probably the least bad option.
Tl;dr. Managing time and daylight savings has long been solved in computer systems. But not for a simple standalone clock.
I have a coffee maker and microwave oven that run off AC and both have clocks. After a momentary power outage the coffee maker will display the correct time * but the microwave will show a flashing 00:00.
*or at least the time the power went out. If the time advanced from 1:32 to 1:33 during that momentary power outage I don’t know if it’ll be a couple seconds slow or not when the power returns.
This is the first I’ve ever heard of a clock that flashes but still shows the correct(ish) time. I’ve only seen ones that either keep going on their merry way after a short blip (my bedside clock radio has a backup 9v battery that will keep the black and white LCD display going but not the backlight, its primary purpose is to power the alarm speaker) or they reset to 12:00 blinking and sit there at 12:00 until you set the time. I’ve also never experienced one that advances the time after 12:00. Interesting.