What is a VALID correct time source?

The reason I ask is because I have a watch (a Casio Waveceptor) that resets itself every night during the night based on a signal sent out by the US Naval Observatory Master Clock at several 1-hr intervals starting at 2AM. I also have an "atomic closk" on the wall of my hobby room that does the same thing. Both of those devices are exactly in sync, as they should be.

Now, all of our cell phones and computers are also in sync, but about a minute or so behind as they sync up with some other source! Wouldn't you think they would all be together, using the US Naval Obervatory's master clock as THE time standard? Why the discrepancy?

For folks who need access to the "CORRECT" time, who do you use?

Thanks!

This:

NIST Time servers

NIST is the official time standard for the USA.

(Stoic-one beat me by a second.)

This is what I use:

http://www.time.gov/

It seems "official" enough for me.

quote:

Originally posted by GaryBF:
This is what I use:

http://www.time.gov/

It seems "official" enough for me.

It is, it sync's with the NIST time servers.

Yup, I've always used NIST time.

those atomic closks are the Chinese versions and not accurate.

What difference, at this time, does it make?

Just a quick comment, but sometimes cell phones will tend to lag for a couple reasons:
1. They're phones, not clocks.
2. There can be some propagation delay pushing the time sync through a cellular network.

I would think they would still be accurate within 30 seconds or so.

Tune in WWV on your short wave radio.

https://en.wikipedia.org/wiki/WWV_(radio_station)

Years ago before the internet I used to tune in the wwv time signal at 10 or 15 mhz to set my watches.

quote:

Originally posted by chellim1:
What difference, at this time, does it make?

Does anybody really know what time it is?
Does anybody really care?
If so I can't imagine why ...
We've all got time enough to cry

I'm retired and don't much give a shit. I don't even own a watch. Or cell phone. They discontinued that when I left. But like Crocodile Dundee, I look outside and see if its day light or dark. If its dark and I'm awake, I need a drink. If its daylight, I need to look for a drink. All this time stress isn't killing me. My rule of thumb (the thickness of a branch that's proper for beating one's wife) is if I need to be somewhere, someone with a lot more stress will tell me.

quote:

Originally posted by stoic-one:
<snip>
2. There can be some propagation delay pushing the time sync through a cellular network.
<snip>

There is indeed some delay in the cellular and wired networks. But it's not nearly as much as "about a minute or so" that Bronica Bill mentions. More on the order of milliseconds.

quote:

Now, all of our cell phones and computers are also in sync, but about a minute or so behind...

Call the WWV dial-up number (303) 499-7111 and listen while observing the clock on your computer expanded to show seconds. There should be less than a second difference. No way there will (should) be 1 minute.

The most accurate time tick is the WWV HF broadcast signal at 2.5, 5, 10, or 15 Mhz. It is not a digital signal and therefore is not "clocked through" countless times on its way to you and therefore is not delayed as are the terrestrial and digital wireless networks.

You can also set up your PC to use an NTP (network time protocol) server. There's various tiers of servers that computers will periodically check in with, and they're very accurate.

Your operating system probably has an "update time and date" button in its clock software somewhere that will reach out to an NTP server and adjust the time to be correct, including accounting for network delay.

If you have a Linux machine handy, it's almost certainly set up for this already and you can just run the 'date' command to see the correct time.

I have three watches that sync to the Atomic clock. My cell phone clicks the hour at the same time they do.

quote:

Originally posted by Jim Shugart:
NIST is the official time standard for the USA.

This is interesting to me. I've got a pair of PLCs at work that are great for short-duration timers, but they suck as clocks. Each week I sync them to the USNO clock. Maybe I'll switch to NIST... not that a second or five here and there matters.

In this particular case, all that matters is that these two devices are reasonably close to actual time, and within a second or two of each other.

I don't like the NIST site/widget much.

I've had good luck with Time.IS

quote:

Originally posted by stoic-one:
Just a quick comment, but sometimes cell phones will tend to lag for a couple reasons:
1. They're phones, not clocks.
2. There can be some propagation delay pushing the time sync through a cellular network.

I would think they would still be accurate within 30 seconds or so.

Then the devices are not doing the math needed to calculate the propagation delay to adjust.

Once upon a time, you could dial P O P C O R N from your rotary phone to get the current time... I also remember listening to my dad's shortwave radio tuned to a station that gave constant time updates. Fun stuff!