What time is it? How do you determine the current, precise time?

Factual Questions
1

Does anyone else here like to know the current, precise time down to the second? How do you determine that? Besides on a smart phone or watch, that is, down to the exact second?

I’m confident this has been discussed here before but I tried searching on time, on atomic time, and on current time and was unable to find it sifting through the many hits, so here goes…

I usually go to the NIST US Dept of Commerce site at ➜ https://time.gov ■ , and this does provide the precise time. Alternately for many years I used to also use the USNO site, the US Naval Observatory’s master clock time. But that URL has changed and the USNO has rearranged their web site since I last went there some years ago. The old URL was
➜ http://www.usno.navy.mil/USNO/time/display-clocks/simpletime ■ ,
but now that remaps to
➜ https://www.cnmoc.usff.navy.mil/usno ■ ,
and I’m having trouble finding their display of the current time. Where is that? (link, please)

I remember that time.gov and the USNO’s clocks matched exactly.

I wear an old fashioned (e.g., not-smart) wrist watch and I like to keep it current and accurate to within seconds of the official atomic time. It’s a quartz watch that is good at maintaining accurate time, usually drifting only a second or two each month.

I actually have two wrist watches, one for every day wear and my other one is an inexpensive solar backup. I like to hack them and keep them both accurate to within seconds. I know there are atomic, solar wrist watches out there but I like my inexpensive solar backup nice enough so I’m not looking to change that. And I’m also not interested in moving to a smart watch, at least not yet. Call me old fashioned.

Also, interestingly, I frequently listen to CBS News Radio (KCBS in San Francisco, 740 AM and 106.9 FM) and every hour on the hour they play a chime, a ding, at exactly on the hour. But for a long time lately that ding has consistently been about 10 or 15 seconds late. I wonder why that is? I haven’t tried searching for the answer but I imagine the reason is out there somewhere. Does anyone know?

Web sites are so much more convenient than in the old days when I’d dial “POPCORN time”, 767-2676 in any area code, to get the current, accurate time down to the seconds. POPCORN time still works but they don’t provide the seconds any more, at least for 408 and 415. Annoyingly, they now make you listen to a commercial.

Thanks in advance.

2

I sync cameras to time.gov especially when working with others and that works great. At other times I have my phone and Apple Watch and don’t particularly care about other clocks (like on appliances) drifting.

3

A GPS unit will have the precise time, because differences in reported time from various satellites is how it determines where you are.

There used to be a time phone number when I was a kid that I would call, I think run by the phone company.

My guess as to why the chimes are off is that everything is going through a censor to beep anything bad, plus delays in turning their signal into digital HD signals?

Anyway, one FQ answer is GPS receivers, which will definitely have a very precise time.

4

I don’t exclude any of your “besides” cases, since my phone is synced to my household server when I’m at home, and the household server is synced to stratum 2 Network Time Protocol servers over the Internet, so the local time source is specified to be accurate to within 100 ms. And my phone is my primary timekeeping device anyway.

As to the USNO master time, I don’t see any sign that they have a public web displayed clock like they used to.

5

My grandfather always said: “A man with one watch always knows what time it is; a man with two is never sure.”

6

The time on the phone was reported every 10 seconds. IIRC the pleasant recorded voice would mark the time with the word ‘exactly’, IOW ‘The time is now 10:56 and 10 seconds exactly’.

7

You are not wrong here. Electric clocks are tuned to 60hz cycles from the mains. Problem is, those 60hz cycles tend to vary and are not always ‘exactly’ 60 hz. It used to be that the power companies would actively compensate to keep the cycles consistent.

But that is expensive and not easy to do. So some years ago, they stopped actively maintaining 60hz with corrections…

8

You can still call NIST (National Institute of Standards and Technology…the people who run the US atomic clocks) to get the time (I doubt you can get more accurate than this…it is an automated system):

303-499-7111 (Colorado)

They also have a radio broadcast.

NIST radio station WWV broadcasts time and frequency information 24 hours per day, 7 days per week to millions of listeners worldwide. WWV is located near Fort Collins, Colorado, about 100 kilometers north of Denver. The broadcast information includes time announcements, standard time intervals, standard frequencies, UT1 time corrections, a BCD time code, and geophysical alerts.

Broadcast Frequencies

WWV operates in the high frequency (HF) portion of the radio spectrum. The station radiates 10 000 W on 5 MHz, 10 MHz, and 15 MHz; and 2500 W on 2.5 MHz and 20 MHz. Each frequency is broadcast from a separate transmitter. Although each frequency carries the same information, multiple frequencies are used because the quality of HF reception depends on many factors such as location, time of year, time of day, the frequency being used, and atmospheric and ionospheric propagation conditions. The variety of frequencies makes it likely that at least one frequency will be usable at all times. - SOURCE

In general though, your phone will have near perfect time (to within a few seconds) since it is updated regularly by your cell carrier. I just called an saw my phone is a few seconds fast (like 2 seconds).

9

Would that affect a radio station’s chime, though? I would think those would be synced to a computer and system clock (usually connected to a time server) and not synced to the mains in any meaningful way. Broadcast delay sounds most likely to me.

10

I’m pretty shocked by this. Don’t the power companies have to be exactly in time with each other on the grid to avoid canceling each other out?

11

Thread from last year.

Back in 2018 I emailed NIST and inquired about time standards. Here is the response I received from one of their physicists:

If you would like a NIST-traceable standard for calibration of a battery-operated clock, there are a few alternatives you might consider. One is a clock or watch that receives WWVB. Another is an ordinary cell phone - presuming that your phone has an app that displays seconds. It’s common practice in cellular telephony to have GPS receivers at the base stations, since the base stations have to be synchronized to a microsecond or better. That’s the time that the base station communicates to the phone. GPS time is traceable to USNO, and NIST and USNO have a memorandum of agreement that our time scales are equivalent to 500 nanoseconds.

12

Curiously, the clock app on my phone (I like to look at an analog dial) is sometimes a few seconds off from the phone’s native time display, which is more accurate.

But I trust my phone to set my wrist watch, and don’t understand why you would exclude that source. I’ve checked my phone’s native time against dedicated time websites, and when my phone is online (usually) that seems to be accurate to the second.

I, too, like to keep my solar-powered dumb wrist watch accurate to within a couple of seconds.

13

I have a solar powered Casio watch that gets the radio signal from NIST I’d guess, and synchs itself in the middle of the night. It has been perfectly accurate for over 20 years now. It blanks out the display for a minute or so while it synchs, which is fine for here but when I take it to Europe happens in the middle of the day, which is annoying.

14

That was a little wishy-washy. You literally can not get more accurate time than from them. They are the US time keeper. When they tell you the time, that is literally the official time.

I would suppose other countries have something similar and maybe they disagree on the time but on microsecond or smaller levels.

In the US, NIST is the official time. As accurate as you can get.

15

How would one go about this?

16

I first heard that from a friend of mine who helped maintain the atomic clocks at the USNO.

17

Aside from my smart phone, I have a clock which syncs to the national time base radio station.

18

One of the nice things about being retired is you don’t have to worry about exact time so much.
I haven’t worn a wristwatch for years.

But for anything that matters, I rely on my computer.
The internet has a standard called Network Time Protocol (NTP) which synchronizes to a global standard to within a few tens of milliseconds.

19

You’re lucky! I wanted that feature and bought a series of those watches, but every one stopped syncing reliably after a couple of years. I must have bought at least 4 or 5 before I finally gave up and bought a Fitbit that syncs with my phone.

20

Some low signal RF systems (long distance shortwave) use a calibrated time base for coordinating send-receive slots. I haven’t used the popular amateur mode JT65 myself but it allows comms well below the noise floor. Most hams just use the Windows clock.