[time-nuts] "Selective availability" af accurate time for Apple users?

Brian Garrett garrettbrian1960 at gmail.com
Tue Oct 20 04:02:13 EDT 2015

Last spring (late March/early April) it was noted on this list  that iPhone clock accuracy had improved significantly with the release of iOS 8.2.  As measured by NTP apps such as Emerald Time and Watchville, millisecond accuracy comparable to the soon-to-be-released Apple Watch was now commonplace, with typical offsets of 5 ms or less, rather than the several seconds of offset typical under the previous release.

Now, with the latest version, iOS 9, the Apple Watch level accuracy previously available to iPhone users has gone away.  Once again, your iPhone will be as much as several seconds slow as measured by NTP, unless you force an update to the phone’s clock by opening a GPS app. It seems that Apple is aware of how they were giving  their highest available accuracy continuously to “mere” iPhone users, and though it cost them nothing to make it available to all, they want to make sure that if you are a _real_ time-nut, you’ll buy an  Apple Watch.

Has anybody else observed this with their iPhone since “upgrading” to iOS 9?   Anyone know of any difference in the reference time ( e.g. GPS vs. network time) that Apple is using to “dumb down’ their smartphones in favor of Apple Watch?

Brian Garrett

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