How much more accurate can the Apple watch be over the iphone time?

Deeds500 · Sep 12, 2014

At the keynote Apple emphasised that its watch will be a precise device. I myself have not worn a watch since I got my first iphone, the 3GS back in 2009. The clock on the iphone has been live on the UI for a couple of years now and the digital clock on the lock screen shows me the time when I request it.

In the time I've relied on the iphone for the time, it has never caused me to be late and I have never missed an appointment as a result of being misinformed of the time from my phone. It also reverts to and from daylight savings when warranted. As far as time keeping is concerned, the iphone does a better than damn good job.

So my question is, how much more accurate than the iphone can the A watch possibly be? Or how much less accurate will the iphone time be? If we're talking 5 seconds over the course of a month or a year then is precision really going to be a point of difference over other time keepers? Yes I know the watch will do alot more than tell the time, but my point is, Apple has done a great job with time keeping on its IOS devices as it is, how much more scope for accuracy can there be?

davidg4781 · Sep 12, 2014

Deeds500 said:
At the keynote Apple emphasised that its watch will be a precise device. I myself have not worn a watch since I got my first iphone, the 3GS back in 2009. The clock on the iphone has been live on the UI for a couple of years now and the digital clock on the lock screen shows me the time when I request it.

In the time I've relied on the iphone for the time, it has never caused me to be late and I have never missed an appointment as a result of being misinformed of the time from my phone. It also reverts to and from daylight savings when warranted. As far as time keeping is concerned, the iphone does a better than damn good job.

So my question is, how much more accurate than the iphone can the A watch possibly be? Or how much less accurate will the iphone time be? If we're talking 5 seconds over the course of a month or a year then is precision really going to be a point of difference over other time keepers? Yes I know the watch will do alot more than tell the time, but my point is, Apple has done a great job with time keeping on its IOS devices as it is, how much more scope for accuracy can there be?

I think they're comparing it to other "normal" watches, or maybe even some "smart" watches.

I know my normal watch is off by a couple of minutes. I don't think it's the battery but it's been probably over a year since I've synchronized it with my iPhone. I also sometimes bump the crown and may have done that to affect the time.

Deeds500 · Sep 12, 2014

davidg4781 said:
I think they're comparing it to other "normal" watches, or maybe even some "smart" watches.

I know my normal watch is off by a couple of minutes. I don't think it's the battery but it's been probably over a year since I've synchronized it with my iPhone. I also sometimes bump the crown and may have done that to affect the time.

So basically, the iphone time is pretty damn accurate, moreso than some dedicated watches.

davidg4781 · Sep 12, 2014

Deeds500 said:
So basically, the iphone time is pretty damn accurate, moreso than some dedicated watches.

One would think so, especially since it's almost always connected to the internet where it can poll NIST or Apple's time servers every hour.

JayLenochiniMac · Sep 12, 2014

They weren't comparing to the time on iPhone.

Julien · Sep 13, 2014

JayLenochiniMac said:
They weren't comparing to the time on iPhone.

This, the time thing is actually more of a fashion statement aimed at luxury watch buyers than a pure tech statement.

kdarling · Sep 13, 2014

Roughly:

- A really good mechanical watch might be accurate to 5 seconds a day.

- Quartz watches are accurate to about 500 ms a day, but try to self-correct every once in a while.

- Apple says their watch time is never off by more than 50 ms.

- Network (NTP) time can be accurate to about 10ms to 100ms.

- Phones usually get their time from the tower's GPS receiver, so they could be accurate in a range of 100ns to 1ms after processing.

--

So it's better than most watches, but much less than a phone, and probably about equal to using NTP on your home computer.

Luba · Sep 14, 2014

Time on a cell phone is that accurate? 1ms? I've noticed in the past 2 cell phones flipping to the next minute at different times, not simultaneously at all. It was something I noticed. I'll pay more attention next time to see if 2 cell phone updates the time simultaneously.

So syncing with NTP is faster than a watch syncing with Universal Time in Colorado, therefore more accurate? I assume NTP is also syncing with Universal Time in Colorado, but it updates to our computers faster than a watch would?

kdarling said:
Roughly:

- A really good mechanical watch might be accurate to 5 seconds a day.

- Quartz watches are accurate to about 500 ms a day, but try to self-correct every once in a while.

- Apple says their watch time is never off by more than 50 ms.

- Network (NTP) time can be accurate to about 10ms to 100ms.

- Phones usually get their time from the tower's GPS receiver, so they could be accurate in a range of 100ns to 1ms after processing.

--

So it's better than most watches, but much less than a phone, and probably about equal to using NTP on your home computer.

kdarling · Sep 14, 2014

Luba said:
Time on a cell phone is that accurate? 1ms? I've noticed in the past 2 cell phones flipping to the next minute at different times, not simultaneously at all. It was something I noticed. I'll pay more attention next time to see if 2 cell phone updates the time simultaneously.

All of these are best case.

For a phone, it would need to be getting time from a CDMA or WCDMA-3G tower, since those need GPS timing. It's quite possible that on some phone networks, the time comes from elsewhere. Or perhaps the phone simply doesn't care about accuracy.

So syncing with NTP is faster than a watch syncing with Universal Time in Colorado, therefore more accurate? I assume NTP is also syncing with Universal Time in Colorado, but it updates to our computers faster than a watch would?

I apologize; I don't understand the question.

The numbers I dug up are about relative accuracy of a time source, not the speed of updating. And of course, if you only updated once a year, your accuracy would suffer appropriately.

I don't have a figure for using the atomic time from Boulder. I would presume the accuracy would all depend on the device itself. For instance, my wall clock that uses Boulder radio signals only cares about displaying time to the second.

Remember, it all also depends on how fast the device's CPU deciphers and/or updates itself and its display.

Julien · Sep 14, 2014

Luba said:
Time on a cell phone is that accurate? 1ms? I've noticed in the past 2 cell phones flipping to the next minute at different times, not simultaneously at all. It was something I noticed. I'll pay more attention next time to see if 2 cell phone updates the time simultaneously....

GPS position is calculated by time. GPS devices sync with GPS satellites. Anytime you use Maps or any App that access GPS its clock is automatically set. If your GPS device is wrong then your location is wrong.

Luba · Sep 14, 2014

I was thinking that NTP sets its time with Boulder, just like a watch would. But time info sync faster through the internet to our computers than through radio signals to a watch.

So actually 2 questions. Does NTP gets its time info from Boulder?

Is the internet faster than radio in syncing the time data?

In the grand scheme of things not important, but cool to know what device has the closest time to the atomic clock in Boulder.

kdarling said:
I apologize; I don't understand the question.

The numbers I dug up are about relative accuracy of a time source, not the speed of updating. And of course, if you only updated once a year, your accuracy would suffer appropriately.

I don't have a figure for using the atomic time from Boulder. I would presume the accuracy would all depend on the device itself. For instance, my wall clock that uses Boulder radio signals only cares about displaying time to the second.

Remember, it all also depends on how fast the device's CPU deciphers and/or updates itself and its display.

Julien · Sep 14, 2014

Luba said:
I was thinking that NTP sets its time with Boulder, just like a watch would. But time info sync faster through the internet to our computers than through radio signals to a watch.

So actually 2 questions. Does NTP gets its time info from Boulder?

Is the internet faster than radio in syncing the time data?

In the grand scheme of things not important, but cool to know what device has the closest time to the atomic clock in Boulder.

For a basic understanding of GPS time read here.

Micky Do · Sep 14, 2014

Deeds500 said:
I myself have not worn a watch since I got my first iphone, the 3GS back in 2009. The clock on the iphone has been live on the UI for a couple of years now and the digital clock on the lock screen shows me the time when I request it.

In the time I've relied on the iphone for the time, it has never caused me to be late and I have never missed an appointment as a result of being misinformed of the time from my phone.

So my question is, how much more accurate than the iphone can the A watch possibly be?

I myself have not worn a watch since my last waterproof one proved better at keeping water in than out, back in 1981. Neither do I carry a phone, simple or smart, tablet, or any other teller of time.

In that time I've relied on the odd glance at a clock and gut feeling; it has never caused me to be late. I have never missed an appointment as a result of being misinformed of the time from what is going on around me. I am known for being on time.

So my question is, how much more accurate timekeeping device toting folks often turn up late?

I woke up not long ago….. gut feeling is that it is breakfast time.

Luba · Sep 14, 2014

Interesting read! It didn't talk about what method was faster in syncing time to devices: internet used by computers vs. radio signals used by watches.

But introduced to me a whole bunch of other things I didn't consider: syncing Universal Time with GPS time, leap seconds, different versions of Universal Time, which I now know why they say Coordinated Universal Time (UTC).

Julien said:
For a basic understanding of GPS time read here.

impaler · Sep 14, 2014

Deeds500 said:
At the keynote Apple emphasised that its watch will be a precise device.

This comment during the keynote kind of threw me for a loop. My phone is synced to the cell tower and the cellular network, regularly - I'm guessing using NTP - which can be GPS or cesium-based. More and more timing and sync solutions are going to cesium, including the Naval Observatory official clock. Point is - if the watch is synced to the tethered phone, won't it just be as accurate as the phone is? I remember something about it changing time zones correctly when you move. It remains to be seen, but it seem 50ns (or ms?) was an unnecessary addition.

Luba · Sep 14, 2014

Cesium-based means atomic clock?

impaler said:
This comment during the keynote kind of threw me for a loop. My phone is synced to the cell tower and the cellular network, regularly - I'm guessing using NTP - which can be GPS or cesium-based. More and more timing and sync solutions are going to cesium, including the Naval Observatory official clock. Point is - if the watch is synced to the tethered phone, won't it just be as accurate as the phone is? I remember something about it changing time zones correctly when you move. It remains to be seen, but it seem 50ns (or ms?) was an unnecessary addition.

impaler · Sep 14, 2014

Luba said:
Cesium-based means atomic clock?

Yes

JayLenochiniMac · Sep 14, 2014

impaler said:
This comment during the keynote kind of threw me for a loop. My phone is synced to the cell tower and the cellular network, regularly - I'm guessing using NTP - which can be GPS or cesium-based. More and more timing and sync solutions are going to cesium, including the Naval Observatory official clock. Point is - if the watch is synced to the tethered phone, won't it just be as accurate as the phone is? I remember something about it changing time zones correctly when you move. It remains to be seen, but it seem 50ns (or ms?) was an unnecessary addition.

If you read this thread, you'll see they weren't comparing to the time on iPhone or any computer that syncs to atomic clock.

impaler · Sep 14, 2014

I did read the thread. I keyed on one aspect of what was said at the keynote.

kdarling · Sep 14, 2014

Luba said:
I was thinking that NTP sets its time with Boulder, just like a watch would. But time info sync faster through the internet to our computers than through radio signals to a watch.

Of course, only a watch with a radio could directly receive the time that way. The Apple Watch no doubt gets it from the phone it's paired to.

So actually 2 questions. Does NTP gets its time info from Boulder?

Partly depends on the network. A company internal network might have its own server, which does get it originally from there. Or you could end up talking directly to an NTP server that gets its time from Colorado, or someplace in Europe (I forget where) or from a GPS receiver.

Is the internet faster than radio in syncing the time data?

Well, I'm near New York City, so it takes the Colorado radio wave about 8ms to reach me. The internet would be slower by anywhere from a few ms to a hundred ms.

Software tries to compensate by testing with pings. But that's why internet NTP is generally considered to only be accurate to about 10ms or more.

Of course, for a watch, being good to a second should be perfectly fine.

Micky Do said:
So my question is, how much more accurate timekeeping device toting folks often turn up late?

You know, it's funny. When I was growing up, it was considered normal for people to be early or late by five or more minutes, simply because that's how accurate our watches were.

Then the quartz watches hit. Oh my. Suddenly you were expected to be on time within seconds.

I think it destroyed civilization

itjw · Oct 8, 2014

My Rolex DateJust is a HORRID keeper of time. It probably needs a servicing honestly (it's been a few years), but it loses about 10-15 seconds a day.

I'm sure a Timex would keep better time.

But it's a Timex. I have a Rolex. It's a different animal.

It's NOT about the incredible precision (even with superlative chronometers). It's about how incredible it is for a mechanical watch without a battery supplying it power to have accuracy within a few seconds a day.

I EXPECT a digital watch to be accurate. It's different technology. Like comparing a steam locomotive to a big rig. Sure, they both transport stuff from point A to point B by land, but that's about it. The Apple watch better be accurate, or it'd be a pretty sad statement...

SHNXX · Oct 11, 2014

Do you really care about 0.1-10 seconds per day?

Yakibomb · Oct 15, 2014

SHNXX said:
Do you really care about 0.1-10 seconds per day?

0.1 seconds no. But 10 seconds per day is about an hour over the year if i'm not mistaken. That could lead to some issues

EDIT: I just remembered that it'll be connecting with the phone multiple times a day, so it'll constantly adjust for the time it's loosing.

HereBeMonsters · Oct 16, 2014

itjw said:
My Rolex DateJust is a HORRID keeper of time. It probably needs a servicing honestly (it's been a few years), but it loses about 10-15 seconds a day.

I'm sure a Timex would keep better time.

But it's a Timex. I have a Rolex. It's a different animal.

It's NOT about the incredible precision (even with superlative chronometers). It's about how incredible it is for a mechanical watch without a battery supplying it power to have accuracy within a few seconds a day.

I EXPECT a digital watch to be accurate. It's different technology. Like comparing a steam locomotive to a big rig. Sure, they both transport stuff from point A to point B by land, but that's about it. The Apple watch better be accurate, or it'd be a pretty sad statement...

That definitely needs something - if not a service then a calibration and adjustment. I have sub $50 Seiko automatics that are more accurate!

firewood · Nov 2, 2014

itjw said:
My Rolex DateJust is a HORRID keeper of time. ...
I'm sure a Timex would keep better time.

My old Bulova automatic kept far better time than my Rolex.

Reason was I would check the old Bulova against WWV radio every night and complain to the watch shop if it drifted by more than 2 or 3 seconds. They would then tweak its calibration for free. But getting my Rolex adjusted seems to cost more than an entire new Bulova automatic, so it rarely goes into the shop.

The Apple watch likely gets its time from an iPhone which in turn gets it time from GPS or the nearest cell tower, if either is available, one or more times per day. GPS time accuracy is well under a millisecond, or else it would put you in the wrong city.

The biggest Apple watch time error likely comes from the watch's GPU pipeline and frame rate, introducing some multiple of 60 Hz quantization error, since I doubt the display frame rate is locked to GPS time. 3 video frames is about 50 mS.

How much more accurate can the Apple watch be over the iphone time?

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