On Sat, Mar 18, 2017 at 2:52 PM, John Hawkinson <jhawk@mit.edu> wrote: > Chris Albertson <albertson.chris@gmail.com> wrote on Fri, 17 Mar 2017 > at 14:38:17 -0700 in <CABbxVHsRa41HoB=xu4nk4T_c39uh2BCOMu17Nb7H3rA8uHXLQg@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... Cheers > 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@mit.edu > John Hawkinson > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there.

		Attila Kinali

On Sun, 26 Mar 2017 16:29:10 +0100 shouldbe q931 <shouldbeq931@gmail.com> wrote: > 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... Ok.. to get this back on a bit more time-nutty things: Modern cell phone protocols either require or contain provisions to diseminate local (and UTC) time to the cellphones. This is also being used as a timing standard for situations where LF stations (WWVB/DCF/..) are not good enough, but no GPS antenna can be used for whatever reason. I most civilized countries this timing code will be quite accurate, down to the µs level. But there are a lot countries where you cannot expect the time code to be anywhere close to reality. E.g. Networks in India are known for transmitting time codes that are multiple minutes off and nobody cares about correcting that. Attila Kinali -- It is upon moral qualities that a society is ultimately founded. All the prosperity and technological sophistication in the world is of no use without that foundation. -- Miss Matheson, The Diamond Age, Neil Stephenson