# How do I determine correct time and recalibrate when my devices show a difference? **URL:** \ **Category:** Factual Questions\ **Created:** [August 26, 2024, 8:37pm UTC](https://boards.straightdope.com/t/how-do-i-determine-correct-time-and-recalibrate-when-my-devices-show-a-difference/1006268 "2024-08-26T20:37:16Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![drad\_dog](https://avatars.discourse-cdn.com/v4/letter/d/aeb1de/32.png) [@drad\_dog](https://boards.straightdope.com/u/drad_dog)\ **Post date:** [August 26, 2024, 8:37pm UTC](https://boards.straightdope.com/t/how-do-i-determine-correct-time-and-recalibrate-when-my-devices-show-a-difference/1006268/1 "2024-08-26T20:37:16Z")
That’s it. My phone and my car are off, and both are off from my PC. ---
**Author:** ![Dewey\_Finn](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dewey_finn/32/4222_2.png) [@Dewey\_Finn](https://boards.straightdope.com/u/Dewey_Finn)\ **Post date:** [August 26, 2024, 8:41pm UTC](https://boards.straightdope.com/t/how-do-i-determine-correct-time-and-recalibrate-when-my-devices-show-a-difference/1006268/2 "2024-08-26T20:41:17Z")
In the US, the [time.gov](http://time.gov) website will give the correct time, and there are similar sites in other countries. Also, my cell phone has, as far as I know, the correct time displayed and my PC can be set to calibrate automatically. ---
**Author:** ![susan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/susan/32/17537_2.png) [@susan](https://boards.straightdope.com/u/susan)\ **Post date:** [August 26, 2024, 8:42pm UTC](https://boards.straightdope.com/t/how-do-i-determine-correct-time-and-recalibrate-when-my-devices-show-a-difference/1006268/3 "2024-08-26T20:42:03Z")
> **[The Official U.S. Time | NIST](https://www.time.gov/)** > > The National Institute of Standards and Technology - Time and Frequency Division maintains the standard for frequency and time interval for the United States, provides official time to the United States, and carries out a broad program of research... will give you the time. Recalibration will depend on the devices. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [August 26, 2024, 8:44pm UTC](https://boards.straightdope.com/t/how-do-i-determine-correct-time-and-recalibrate-when-my-devices-show-a-difference/1006268/4 "2024-08-26T20:44:22Z")
Recalibrate what? Your phone probably has the most accurate time since it gets it from the cell network and is updated on a regular basis. Or, you can use the time from the US atomic clocks run by NIST: > **[The Official U.S. Time | NIST](https://www.time.gov/)** > > The National Institute of Standards and Technology - Time and Frequency Division maintains the standard for frequency and time interval for the United States, provides official time to the United States, and carries out a broad program of research... And, if you are really old school, you can dial 202-762-1401 for the current time run by the US Naval Observatory. (Kind of amazed that still works…I just called it and it is a blast from the past.) ETA: Ninjaed for being thorough. ---
**Author:** ![Kedikat](https://avatars.discourse-cdn.com/v4/letter/k/ed655f/32.png) [@Kedikat](https://boards.straightdope.com/u/Kedikat)\ **Post date:** [August 26, 2024, 8:59pm UTC](https://boards.straightdope.com/t/how-do-i-determine-correct-time-and-recalibrate-when-my-devices-show-a-difference/1006268/5 "2024-08-26T20:59:49Z")
One with two clocks, is never sure what time it is. But these days you can easily get within a few nanoseconds. GPS time. I am always calibrating devices with the GPS pulse per second feature. Of course you can’t press a button on your gadget to get nano close. But if you have access to a GPS device that shows time. You are fine. As mentioned, cell phone is fine too. But be careful when near a time zone border area. It can flip an hour here and there along that line. Half an hour here and there too. We also use the same devices that server farms and such use to sync things. GPS based as well. One is called Time Machine. ---
**Author:** ![markn\_1](https://avatars.discourse-cdn.com/v4/letter/m/f9ae1b/32.png) [@markn\_1](https://boards.straightdope.com/u/markn_1)\ **Post date:** [August 26, 2024, 9:00pm UTC](https://boards.straightdope.com/t/how-do-i-determine-correct-time-and-recalibrate-when-my-devices-show-a-difference/1006268/6 "2024-08-26T21:00:06Z")
It’s strange that your phone and PC disagree. Both should be getting the time from a time server. Assuming your PC is running Windows, open Control Panel, select Clock and Region → Date and Time → Internet Time → Change settings, and make sure that “Synchronize with an Internet time server” is checked. ---
**Author:** ![jnglmassiv](https://avatars.discourse-cdn.com/v4/letter/j/f07891/32.png) [@jnglmassiv](https://boards.straightdope.com/u/jnglmassiv)\ **Post date:** [August 26, 2024, 9:13pm UTC](https://boards.straightdope.com/t/how-do-i-determine-correct-time-and-recalibrate-when-my-devices-show-a-difference/1006268/7 "2024-08-26T21:13:17Z")
US Government’s NIST operates the WWV transmitters that say the time, in plain, spoken English on 5, 10, 15 & 20 MHz. Just tune in and listen! ---
**Author:** ![Dewey\_Finn](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dewey_finn/32/4222_2.png) [@Dewey\_Finn](https://boards.straightdope.com/u/Dewey_Finn)\ **Post date:** [August 26, 2024, 9:17pm UTC](https://boards.straightdope.com/t/how-do-i-determine-correct-time-and-recalibrate-when-my-devices-show-a-difference/1006268/8 "2024-08-26T21:17:31Z")
It’s so cute how optimistic you are that someone would still have a shortwave radio. ---
**Author:** ![jnglmassiv](https://avatars.discourse-cdn.com/v4/letter/j/f07891/32.png) [@jnglmassiv](https://boards.straightdope.com/u/jnglmassiv)\ **Post date:** [August 26, 2024, 9:24pm UTC](https://boards.straightdope.com/t/how-do-i-determine-correct-time-and-recalibrate-when-my-devices-show-a-difference/1006268/9 "2024-08-26T21:24:22Z")
I’m just giving OP their requested options. > [@Whack-a-Mole](#): > > And, if you are really old school, you can dial 202-762-1401 for the current time run by the US Naval Observatory Hey, so does 303/499-7111! Beee-beeeee-beeee ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [August 26, 2024, 9:26pm UTC](https://boards.straightdope.com/t/how-do-i-determine-correct-time-and-recalibrate-when-my-devices-show-a-difference/1006268/10 "2024-08-26T21:26:02Z")
> [@jnglmassiv](#): > > US Government’s NIST operates the WWV transmitters that say the time, in plain, spoken English on 5, 10, 15 & 20 MHz. Just tune in and listen! Didn’t there used to be table clocks (digital) that could listen to that signal and keep their time accurate? ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [August 26, 2024, 9:31pm UTC](https://boards.straightdope.com/t/how-do-i-determine-correct-time-and-recalibrate-when-my-devices-show-a-difference/1006268/11 "2024-08-26T21:31:18Z")
I called that one…sounds even more old school. I noticed that my time on my computer was almost perfectly synched since I have the PC setup as @markn_1 mentioned (not to the nanosecond or millisecond but it seemed within a half-second or so). Plenty good enough for my needs. ---
**Author:** ![drad\_dog](https://avatars.discourse-cdn.com/v4/letter/d/aeb1de/32.png) [@drad\_dog](https://boards.straightdope.com/u/drad_dog)\ **Post date:** [August 26, 2024, 9:41pm UTC](https://boards.straightdope.com/t/how-do-i-determine-correct-time-and-recalibrate-when-my-devices-show-a-difference/1006268/12 "2024-08-26T21:41:00Z")
Nah. My phone was wrong and I reset it, which turned out to be easy. The PC is auto updated. Now about my damned car… ---
**Author:** ![drad\_dog](https://avatars.discourse-cdn.com/v4/letter/d/aeb1de/32.png) [@drad\_dog](https://boards.straightdope.com/u/drad_dog)\ **Post date:** [August 26, 2024, 9:41pm UTC](https://boards.straightdope.com/t/how-do-i-determine-correct-time-and-recalibrate-when-my-devices-show-a-difference/1006268/13 "2024-08-26T21:41:39Z")
half a sec is fine by me. I’m talking a minute or more. ---
**Author:** ![BigT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bigt/32/12044_2.png) [@BigT](https://boards.straightdope.com/u/BigT)\ **Post date:** [August 26, 2024, 9:45pm UTC](https://boards.straightdope.com/t/how-do-i-determine-correct-time-and-recalibrate-when-my-devices-show-a-difference/1006268/14 "2024-08-26T21:45:28Z")
> [@drad\_dog](#): > > Nah. My phone was wrong and I reset it, which turned out to be easy. The PC is auto updated. > > Now about my damned car… ⁢ Yeah, phones can definitely be wrong, as they only update the time when you restart them (using NIST) or when you get a call (from the Caller ID). The car has nothing to keep it in sync, most likely. So your PC is the best bet, especially if you click on the clock, open Date and Time, and then click “Sync Now.” Though usually rebooting your phone would have also worked, assuming it has Internet access. ---
**Author:** ![drad\_dog](https://avatars.discourse-cdn.com/v4/letter/d/aeb1de/32.png) [@drad\_dog](https://boards.straightdope.com/u/drad_dog)\ **Post date:** [August 26, 2024, 9:46pm UTC](https://boards.straightdope.com/t/how-do-i-determine-correct-time-and-recalibrate-when-my-devices-show-a-difference/1006268/15 "2024-08-26T21:46:35Z")
My shortwave radio has fibber mcgee and molly on it. Can’t tell the time but I’m doubtful. ---
**Author:** ![markn\_1](https://avatars.discourse-cdn.com/v4/letter/m/f9ae1b/32.png) [@markn\_1](https://boards.straightdope.com/u/markn_1)\ **Post date:** [August 26, 2024, 9:51pm UTC](https://boards.straightdope.com/t/how-do-i-determine-correct-time-and-recalibrate-when-my-devices-show-a-difference/1006268/16 "2024-08-26T21:51:14Z")
I wrote a simple NTP client once; I think it was for ReplayTV. It’s difficult to get millisecond level accuracy by asking a server for the time, when the Internet connection itself may have multiple-millisecond latency. The NTP protocol has a built-in mechanism to account for the latency but it works well only if the latency remains constant for the request and response. But accuracy on the level of a few tens of milliseconds is usually doable unless the connection is very flakey. Clock accuracy is impacted more by drift of the device’s clock hardware between NTP requests. ---
**Author:** ![kenobi\_65](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kenobi_65/32/13178_2.png) [@kenobi\_65](https://boards.straightdope.com/u/kenobi_65)\ **Post date:** [August 26, 2024, 9:55pm UTC](https://boards.straightdope.com/t/how-do-i-determine-correct-time-and-recalibrate-when-my-devices-show-a-difference/1006268/17 "2024-08-26T21:55:39Z")
> [@drad\_dog](#): > > My shortwave radio has fibber mcgee and molly on it. Can’t tell the time but I’m doubtful. According to your radio, it must be 1947. 😉 ---
**Author:** ![jnglmassiv](https://avatars.discourse-cdn.com/v4/letter/j/f07891/32.png) [@jnglmassiv](https://boards.straightdope.com/u/jnglmassiv)\ **Post date:** [August 26, 2024, 11:23pm UTC](https://boards.straightdope.com/t/how-do-i-determine-correct-time-and-recalibrate-when-my-devices-show-a-difference/1006268/18 "2024-08-26T23:23:46Z")
> [@Whack-a-Mole](#): > > I called that one…sounds even more old school. It didn’t occur to me that they’d be different announcements earlier but, having just phoned and listened to each, 303 WWV is what you hear over the air with most of the message a nonverbal audio tone. I’ve heard it for hours and hour, in widely varying audio qualities, while tinkering with radio stuff over the years. > [@Whack-a-Mole](#): > > Didn’t there used to be table clocks (digital) that could listen to that signal and keep their time accurate? Yes and current ones, too. They actually use the longwave 60 kHz station, WWVB: > **[WWVB](https://en.wikipedia.org/wiki/WWVB)** > > WWVB is a time signal radio station near Fort Collins, Colorado and is operated by the National Institute of Standards and Technology (NIST). Most radio-controlled clocks in North America use WWVB's transmissions to set the correct time. > The normal signal transmitted from WWVB is 70 kW ERP and uses a 60 kHz carrier wave yielding a frequency uncertainty of less than 1 part in 1012. The time code signal is derived from a set of atomic clocks located at the site, and transmitted using the IRIG "H... I forgot there’s a 25 MHz WWV in Colorado, too: > **[Radio clock](https://en.wikipedia.org/wiki/Radio_clock)** > > A radio clock or radio-controlled clock (RCC), and often colloquially (and incorrectly) referred to as an "atomic clock", is a type of quartz clock or watch that is automatically synchronized to a time code transmitted by a radio transmitter connected to a time standard such as an atomic clock. Such a clock may be synchronized to the time sent by a single transmitter, such as many national or regional time transmitters, or may use the multiple transmitters used by satellite navigation systems On... ---
**Author:** ![CaveMike](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cavemike/32/16379_2.png) [@CaveMike](https://boards.straightdope.com/u/CaveMike)\ **Post date:** [August 26, 2024, 11:30pm UTC](https://boards.straightdope.com/t/how-do-i-determine-correct-time-and-recalibrate-when-my-devices-show-a-difference/1006268/19 "2024-08-26T23:30:34Z")
> [@BigT](#): > > Though usually rebooting your phone would have also worked, assuming it has Internet access. Toggling airplane mode should work. The phone will reattach to the network. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [August 26, 2024, 11:35pm UTC](https://boards.straightdope.com/t/how-do-i-determine-correct-time-and-recalibrate-when-my-devices-show-a-difference/1006268/20 "2024-08-26T23:35:49Z")
> [@drad\_dog](#): > > Nah. My phone was wrong and I reset it, which turned out to be easy. That surprises me. The clock signal is part of the wireless protocol I believe. All cell phones get it and I thought all cell phones would update their clocks to the time signal from their cell provider. I haven’t had to update my phone’s clock ever except when on a ship in the middle of the ocean and we moved through time zones (and then the phone was not connected to a cell network). [Next page](https://boards.straightdope.com/t/how-do-i-determine-correct-time-and-recalibrate-when-my-devices-show-a-difference/1006268.md?page=2)