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

John Hawkinson jhawk at MIT.EDU
Sat Mar 18 10:52:31 EDT 2017

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

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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