[time-nuts] Striking change in iPhone time accuracy with 8.2

Reid Oda reid.oda at gmail.com
Wed Apr 1 12:33:20 EDT 2015


First email to the list here. I've been curious about this for a little
while: does the iPhone get sub-second timing info from GPS?

I did an experiment the other day where my friend and my iPhone clocks had
a fairly large offset, of perhaps 0.3 seconds. We were away from any

We went to a window, and watched as the Google maps location estimate got
to its most accurate setting. I assume the estimate accuracy is based on
the number of satellites the phone can see. Once we got this lock, the
clocks were then synchronized to within a few ms of each other. I estimate
8 ms, but our method (listening to ticks from a homemade app) was not ultra

This seems to imply that the iPhone does get sub-second timing info from
GPS. Can anyone confirm/deny this?

On Wed, Apr 1, 2015 at 8:03 AM, Raj <vu2zap at gmail.com> wrote:

> Now that you mention it!
> I use the app Emerald Sequoia watch that gives me time from 4 servers but
> it does not change the phone time.
> Seconds to one decimal place.
> Raj, vu2zap
> At 01/04/2015, you wrote:
> >Has anyone else noticed a dramatic improvement in the accuracy of time
> >of day on iPhones and iPads since the release of iOS 8.2? The accuracy
> >used to be only plus or minus 2 or 3 seconds, now it is about 100
> >times better, usually a few tens of milliseconds. I figure Apple might
> >have finally paid some attention to accurate time of day with 8.2,
> >possibly because of the Apple Watch. It's a pleasing improvement, I
> >hope it's permanent.
> >
> >--
> >Anthony
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