[time-nuts] How are iPhones' clocks set under LTE?

Chris Albertson albertson.chris at gmail.com
Sun Aug 3 19:40:36 EDT 2014

IOS is getting the time using the IP network which is above the CDMA
or WiFi level.  It polls an NTP server just frequently enough to keep
the system clock to within "a few seconds" of correct time.

I could run the full NTP but doesn't because that would drain the
battery to fast.  Background tasks mean the CPU can't go into sleep

The phone has the GPS receiver too and I'm a little surprised they
don't get the time from GPS.  But it is all about battery life and
there is no need to run the GPS if the phone is not moving.

On Sun, Aug 3, 2014 at 1:37 PM, Brian Garrett
<garrettbrian1960 at gmail.com> wrote:
> Hi all,
> First “time”r here.  This may not rank up there with your degree of time-nuttery, but I haven’t been able to get an answer elsewhere.  Recently I was discussing the issue of how the different cellular providers set their time, and I told him that I’d read that CDMA phones and towers have to have their clocks synced to GPS as part of the protocol,


Chris Albertson
Redondo Beach, California

More information about the time-nuts mailing list