[tz] If you lie about the time zone, your iPhone will have its revenge

Guy Harris guy at alum.mit.edu
Mon Jan 18 07:42:27 UTC 2016

On Jan 17, 2016, at 11:14 PM, Paul Eggert <eggert at cs.ucla.edu> wrote:

> iPhone 6s and iPhone 6s Plus users are reporting that their phones are sometimes showing plenty of charge left even though their batteries are actually depleted, leaving some users stranded out of power. Apparently users who change their time (e.g., to gain unfair advantage in games like Candy Crush Saga) can confuse iOS 9.2 into not updating the battery percentage indicator. A similar problem can occur to users who set the time zone manually. One workaround is to reboot and revert to getting date and time from the network.

Or, at least, to do so on iPhone 6s/6s Plus.

This is a bit weird - I'd expect whatever checks the battery to be doing "check every second"-type checks, which *might* be confused if somebody actually did settimeofday() (General -> Date & Time -> turn off "Set Automatically" and then set the time manually), but which I wouldn't expect to be confused by removing /etc/timezone and re-linking it to another file (General -> Date & Time -> turn off "Set Automatically" and then set the time zone automatically).

Then again, if it's only on the 6s models, maybe there's some new hardware in it that somehow has to deal with local time and that gets confused by time zone changes.

(So what happens if whatever daemon is responsible for monitoring your location notices you've crossed a time zone boundary and changes the time zone *for* you?  "Set Automatically" enables that.)

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