Atomic clocks and Daylight Savings

And don’t forget WWVH from Hawaii. Same information and frequincies, but the voice announcements are in a female voice.

Tried this. After I held it for a few seconds, the hands started going, like they were going to reset themselves (and I stood near a window while they were resetting). They came right back to standard time! I’ve tried calling the number on the back of the clock, but it’s still busy. I don’t think Sharp thought the whole time change thing through very well.

My g-shock watch was off by an hour yesterday, but today it was fine. Apparently it syncs up to the signal at midnight, and since at midnight Sunday morning DST hadn’t started yet, it was off by an hour for the day. Maybe your clock only syncs once every few days or something?

I have 2 wall atomic clocks and one alarm atomic clock. All of them reset to the correct DLS time OK.

Apparently not. Well, at least now you know what that button does.

They are set to receive the signal at night time because it is stronger/easier to receive. They do not constantly receive and update. They receive once a day during the night and make small adjustments.
I bet if the OP just waits until tomorrow, it will be reset.

Most VLF consumer devices use ferrite loop stick antennas, for example this VLF watch antenna, or these.

Three of my four “atomic” clocks adjusted themselves correctly early Sunday morning, but the fourth, a Sharp wall clock, like the OP’s, did not. But it is located furthest from the exterior of my house than any of the others. I placed it near a window and it adjusted itself correctly overnight last night. As someone said, they appear to only update around 2 or 3 in the morning. I hope the OP’s clock is okay now.

:frowning: No, it’s not okay. It still has the incorrect time. It’s now sitting patiently in the window, awaiting the signal that will tell it it’s okay to move ahead one hour. Everybody cheer the little guy on. (And, Sharp’s number is still busy.)

You might want to make sure that you press the ET button one more time before your go to bed tonight. You might have accidentally hit the CT button.

If it didn’t update again, you could try rotating it 90 degrees and giving it another chance the next night. The loop antenna is similar to an AM radio antenna, and is sensitive to rotation.

Just in case anyone’s interested, our clock set itself correctly last night - it’s been hanging on the wall all this time, waiting for its cue. The one by our bedside (that I futzed around with and got to give us the correct time) adjusted itself also, to read an hour later (I guess I had set it for Atlantic time). We lazed in bed, thinking how extraordinary it was that both of our kids slept in until 9! Ha!

This is incorrect - the NIST time signals broadcast the year, month, date, hour and minute, every minute.

That probably wasn’t from a radio cue… I think this morning is the time when DST would have started, under the old rules. My office computer (which is running an old OS version, and so didn’t recognize the rule update) is now showing the correct DST time also.

They broadcast UTC. How that is converted to local time is up to the implementor. One way of doing that is to decouple the hours from the minutes and seconds. The time signal is used to keep the minutes and seconds in sync with UTC. The hours are manually set and incremented by the carry from the minutes count. This is similar to the way telegraph lines used to be used to be used to synchronize electro-mechanical clocks. Western Union used to rent clocks that were synchronized daily with the USNO via telegraph line.

See TAKING TIME OUT FOR TIME.