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

shouldbe q931 shouldbeq931 at gmail.com
Sun Mar 26 11:29:10 EDT 2017

On Sat, Mar 18, 2017 at 2:52 PM, 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.

Not all phone networks provide time, I was quite surprised in the 90s
when I crossed the English channel going to France and the time on my
(GSM) phone automatically updated, and just as disappointed when I
returned and the clock did not update, this was of course long before
"smartphones" with GPS or NTP clients...


> 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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