I'm curious how my iPhone knows what time zone I am in and change automatically. Does the phone use GPS to figure out where I am in the world? Or is there some other technology in play here.

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2 Answers 2


It uses a combination of GPS and the date/time sent to the iPhone from the cell towers.

There's several questions here about this same topic (different carriers and different iPhones) and they all have very similar responses to what I've said. If you search for this topic, you can see all the different questions and answers; I just combined them all.

  • Hmm GPS vs cell tower. There must be a definitive answer
    – Sun
    Nov 7, 2016 at 19:54
  • 1
    I don't know if there's just 1 way. It gets location & timestamp from GPS but the time doesn't change instantly when I cross a timezone line. GPS settings might not be exact for any number of reasons. If you're in airplane mode then you're not connected to cell towers so it can't always rely on that. I think the most correct answer is "any combination of the above methods."
    – fsb
    Nov 7, 2016 at 20:09
  • It may also get the time and time zone from a wifi connection. I've setup at least 50 AppleTVs at my school, and each one recognizes the time zone when I tell the ATV to select automatically. This presupposes that the wifi infrastructure is correctly set itself.
    – IconDaemon
    Nov 7, 2016 at 20:53
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    It's tower time. Go out to Hoover Dam ... Your phone changes about 15 miles from the time zone line
    – Tyson
    Nov 7, 2016 at 22:49
  • PART 1 Yes, it does seem to use a combination of GPS and cell towers. I travelled to Central European Time (CET), and the phone had updated to that timezone. I then returned to UK timezone, but I had turned off mobile data for a number of apps (including Settings, which may be critical). The phone did not update from CET to UK timezone, despite using the phone with WiFi for about 12 hours, and despite phones usually determining your location from WiFi.
    – Tim
    Sep 30 at 14:12

It is a SMART PHONE. ( as smart as the person using it. Meaning it has the capacity to do astounding things if you learn how to use it. ) You can use the settings function to set the phone to the time zone you are in and tell it to update automatically or manual. You can set it to a new time zone when you travel.

Settings> general > date and time

if the phone knows what time zone it is in then it know what time it is in that time zone. If you set it to alaska time but you are in new york it will give you the time in alaska ( because you told it is in alaska). If it is set to not set automaticly.

  • Sun asked how it knows what time zone it's in, not how to make it set the time zone automatically.
    – Tuesday
    Nov 7, 2016 at 20:28

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