[time-nuts] Smart Phone time display accuracy...?

Glen Hoag hoag at hiwaay.net
Sat Mar 18 12:37:41 EDT 2017

On my iPhone, I run an NTP client, Emerald Time, that displays the offset between NTP time and the device's internal clock. 

I'm on T-Mobile US and the offset is typically in the low tens of milliseconds or better. 

It's certainly accurate enough as a clock where all I'm looking at is one minute resolution. 

Glen Hoag
hoag at hiwaay.net
Sent from my iPhone

> On Mar 18, 2017, at 09:52, John Hawkinson <jhawk at MIT.EDU> wrote:
> Chris Albertson <albertson.chris at gmail.com> wrote on Fri, 17 Mar 2017
> at 14:38:17 -0700 in <CABbxVHsRa41HoB=xu4nk4T_c39uh2BCOMu17Nb7H3rA8uHXLQg at mail.gmail.com>:
>>> AndroiTS GPS Test (V 1.48 Free) is good, but a battery hog I find.   On
>> THIS is why the phones don't really track time so well.  Not that they
>> can't but doing so requires battery power. 
> This statement doesn't seem to be well-supported. I think it's
> basically untrue if we're talking about timing at the tens of
> millisecond level.  Anything more precise seems relatively useless in
> a smartphone without specialized mechanisms to get the time off of the
> phone.
> A phone's GPS receiver takes a lot of battery. But GPS is not the primary
> mechanism that phones use get their time.
> They get time from the cellular phone network (whether from the layer
> two timing information or at a higher layer with something like
> NTP). The effort required to keep a phone's clock in sync, even with a
> really bad local oscillator, is lost in the noise of all the other
> things the phone has to do. It's just not a battery issue.
> The only reason modern smartphones keep bad time is because their
> designers can't be bothered to do better, or possibly the network is
> providing "bad" time to the phone. (Unless I'm missing something.)
> --jhawk at mit.edu
>  John Hawkinson
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