How does iPhone get the exact right Time and Date

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Level 1

11 points

How does iPhone get the exact right Time and Date

How does iPhone get the exact right Time and Date ?

Even if in an iPhone, we turn on the Airplane mode and take out SIM from the phone and then manually change the Time, Date and Time Zone, the moment you toggle back Automatic Date & Time button, iPhone magically sets back to the exact right Time Date and Time Zone. This happens outside home as well as inside. I can understand that iPhone can decode GPS signals when outside, but how does it correct its system time without any communication. Can anyone explain this spooky behavior?

iPhone 8 Plus, iOS 13

Posted on Jul 7, 2020 2:38 AM

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Answer 1

KiltedTim

Level 10

231,032 points

Jul 7, 2020 8:56 AM in response to Siddze

It picks up the time and date from the cell towers.

It can find and connect to the cellular network even without the SIM.

This is a legal requirement in the US and my other countries as even a deactivated phone without a SIM must be able to call 911 (or the appropriate emergency service number in other countries).

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Answer 2

Siddze Author

Level 1

11 points

Jul 7, 2020 8:51 AM in response to FoxFifth

Thanks for the reply. But how come iPhone & Apple Watch synchronize their system time when inside the home. GPS requires clear view of the sky or at least partial view of the sky for time signal reception. Just try it with your phone.

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Answer 3

FoxFifth

Level 10

476,329 points

Jul 7, 2020 8:15 AM in response to Siddze

I suspect the following is the explanation: https://www.gps.gov/applications/timing/

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How does iPhone get the exact right Time and Date

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