# Atomic clocks and Daylight Savings **URL:** \ **Category:** Factual Questions\ **Created:** [March 11, 2007, 1:55pm UTC](https://boards.straightdope.com/t/atomic-clocks-and-daylight-savings/395485 "2007-03-11T13:55:37Z")\ **Posts on this page:** 15\ **Page:** 2
**Author:** ![GaryM](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/garym/32/241_2.png) [@GaryM](https://boards.straightdope.com/u/GaryM)\ **Post date:** [March 12, 2007, 5:50pm UTC](https://boards.straightdope.com/t/atomic-clocks-and-daylight-savings/395485/21 "2007-03-12T17:50:10Z")
[QUOTE=Scuba\_Ben] An update to my post: NIST’s site for WWVB says that the time signal beacon transmits on 60 kHz. This is in the low frequency band. I’m impressed that they get good propagation on this band, and good reception in consumer electronics. And my memory was not quite right – WWV (as opposed to the beacon station) transmits on 2.5, 5, 10, 15, and 20 MHz. The transmission is a tick every second, voice announcement of each minute, and voice information on propagation conditions. [/QUOTE] And don’t forget WWVH from Hawaii. Same information and frequincies, but the voice announcements are in a female voice. ---
**Author:** ![C3](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/c3/32/3108_2.png) [@C3](https://boards.straightdope.com/u/C3)\ **Post date:** [March 12, 2007, 6:14pm UTC](https://boards.straightdope.com/t/atomic-clocks-and-daylight-savings/395485/22 "2007-03-12T18:14:08Z")
[QUOTE=Q.E.D.] Try pressing and holding that one for a few seconds. [/QUOTE] 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. ---
**Author:** ![audiobottle](https://avatars.discourse-cdn.com/v4/letter/a/bc8723/32.png) [@audiobottle](https://boards.straightdope.com/u/audiobottle)\ **Post date:** [March 12, 2007, 6:17pm UTC](https://boards.straightdope.com/t/atomic-clocks-and-daylight-savings/395485/23 "2007-03-12T18:17:32Z")
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? ---
**Author:** ![lk1932](https://avatars.discourse-cdn.com/v4/letter/l/aeb1de/32.png) [@lk1932](https://boards.straightdope.com/u/lk1932)\ **Post date:** [March 12, 2007, 11:19pm UTC](https://boards.straightdope.com/t/atomic-clocks-and-daylight-savings/395485/24 "2007-03-12T23:19:52Z")
I have 2 wall atomic clocks and one alarm atomic clock. All of them reset to the correct DLS time OK. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [March 12, 2007, 11:27pm UTC](https://boards.straightdope.com/t/atomic-clocks-and-daylight-savings/395485/25 "2007-03-12T23:27:59Z")
[QUOTE=C3] I don’t think Sharp thought the whole time change thing through very well. [/QUOTE] Apparently not. Well, at least now you know what that button does. ---
**Author:** ![Bear\_Nenno](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bear_nenno/32/3358_2.png) [@Bear\_Nenno](https://boards.straightdope.com/u/Bear_Nenno)\ **Post date:** [March 13, 2007, 12:03am UTC](https://boards.straightdope.com/t/atomic-clocks-and-daylight-savings/395485/26 "2007-03-13T00:03:05Z")
[QUOTE=audiobottle] 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? [/QUOTE] 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. ---
**Author:** ![Arjuna34](https://avatars.discourse-cdn.com/v4/letter/a/eb8c5e/32.png) [@Arjuna34](https://boards.straightdope.com/u/Arjuna34)\ **Post date:** [March 13, 2007, 2:02am UTC](https://boards.straightdope.com/t/atomic-clocks-and-daylight-savings/395485/27 "2007-03-13T02:02:54Z")
[QUOTE=Scuba\_Ben] I would expect that practical applications in VLF use something other than a half-wave antenna. [/QUOTE] Most VLF consumer devices use ferrite loop stick antennas, for example this [VLF watch antenna](http://www.c-maxgroup.com/products/showProduct.php?id=19), or [these](http://www.c-maxgroup.com/products/showProduct.php?id=20). ---
**Author:** ![commasense](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/commasense/32/3017_2.png) [@commasense](https://boards.straightdope.com/u/commasense)\ **Post date:** [March 13, 2007, 2:34am UTC](https://boards.straightdope.com/t/atomic-clocks-and-daylight-savings/395485/28 "2007-03-13T02:34:12Z")
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. ---
**Author:** ![C3](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/c3/32/3108_2.png) [@C3](https://boards.straightdope.com/u/C3)\ **Post date:** [March 13, 2007, 2:42am UTC](https://boards.straightdope.com/t/atomic-clocks-and-daylight-savings/395485/29 "2007-03-13T02:42:59Z")
☹ 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.) ---
**Author:** ![commasense](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/commasense/32/3017_2.png) [@commasense](https://boards.straightdope.com/u/commasense)\ **Post date:** [March 13, 2007, 3:00am UTC](https://boards.straightdope.com/t/atomic-clocks-and-daylight-savings/395485/30 "2007-03-13T03:00:46Z")
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. ---
**Author:** ![Arjuna34](https://avatars.discourse-cdn.com/v4/letter/a/eb8c5e/32.png) [@Arjuna34](https://boards.straightdope.com/u/Arjuna34)\ **Post date:** [March 13, 2007, 11:50am UTC](https://boards.straightdope.com/t/atomic-clocks-and-daylight-savings/395485/31 "2007-03-13T11:50:34Z")
[QUOTE=C3] ☹ 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.) [/QUOTE] 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. ---
**Author:** ![C3](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/c3/32/3108_2.png) [@C3](https://boards.straightdope.com/u/C3)\ **Post date:** [April 1, 2007, 3:11pm UTC](https://boards.straightdope.com/t/atomic-clocks-and-daylight-savings/395485/32 "2007-04-01T15:11:39Z")
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! ---
**Author:** ![Absolute](https://avatars.discourse-cdn.com/v4/letter/a/b2d939/32.png) [@Absolute](https://boards.straightdope.com/u/Absolute)\ **Post date:** [April 1, 2007, 4:26pm UTC](https://boards.straightdope.com/t/atomic-clocks-and-daylight-savings/395485/33 "2007-04-01T16:26:17Z")
[QUOTE=Mr. Miskatonic] What they do depends on the design. One I have has a tiny button you hit with a pencil to make the adjustement. The other I have to push some buttons on the back. Neither will adjust itself for daylight savings time. They recieve the minute from the radio frequency and make adjustments, not the hour. [/QUOTE] This is incorrect - the NIST time signals broadcast the year, month, date, hour and minute, every minute. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [April 1, 2007, 4:46pm UTC](https://boards.straightdope.com/t/atomic-clocks-and-daylight-savings/395485/34 "2007-04-01T16:46:59Z")
> [@](#): > > 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. 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. ---
**Author:** ![mks57](https://avatars.discourse-cdn.com/v4/letter/m/b9bd4f/32.png) [@mks57](https://boards.straightdope.com/u/mks57)\ **Post date:** [April 1, 2007, 4:49pm UTC](https://boards.straightdope.com/t/atomic-clocks-and-daylight-savings/395485/35 "2007-04-01T16:49:27Z")
[QUOTE=Absolute] This is incorrect - the NIST time signals broadcast the year, month, date, hour and minute, every minute. [/QUOTE] 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](http://www.imakenews.com/symmtsd/e_article000545011.cfm?x=b11,0,w). [Previous page](https://boards.straightdope.com/t/atomic-clocks-and-daylight-savings/395485.md?page=1)