When I googled earlier, all answers pointed towards the phone receiving cellular signals or depending on its internal digital clock but I’m asking this question because when we crossed my country’s border and briefly entered our neighbor’s territory, my phone’s time automatically changed to the neighboring country’s timezone even though there was absolutely zero cellular service and I didn’t have mobile data or location turned on (not that mobile data would have worked without cell service)
So, how did my phone know the other country’s time? I don’t really understand how the internal clock works either, but this is even more of a mystery to me. Would love to know how this really works!
In: Technology
Did you connect to WiFi at any point after crossing?
At some point your cell phone connected to some kind of service and was able to receive an update about the current time.
GPS or similar positioning system. GPS works by each satellite transmitting its precise orbital parameters and a UTC time, and by comparing the signals from multiple satellites your phone can determine its location on the planet. Because it knows where it is and a UTC time it can compare that against a locally stored map of the time zones to figure out what the proper local time is to display.
I don’t know what setting exactly you mean by “location”, but it’s likely you only turned off the use of local cellular/wifi signals, not GPS itself. So it probably used its internal clock to keep time and the GPS position to set the time zone.
Your phone almost certainly has a built in GPS. Depending on the device, switching off “location services” may shut off access to software, but it is unlikely that the GPS itself is shut off.
So, since the clock is almost certainly part of the OS, it can be given access to all sorts of information that is not being shared with third party apps. Information like the GPS data that’s otherwise being withheld.
Since it cannot be magic, it must have picked up the location from somewhere. Most likely from a cell tower with a signal too weak for it to show as 1 bar service on the display, just a quiet, or brief, message received. Or it does GPS location for “system uses” even when the display says GPS location is switched off.
It’s technically possible that it could use accelerometers, e.g. “if you leave your home and travel 50km/h West, you will be in the next country in 30 minutes”. Possible that it could use mesh networking, like Apple’s air tags, and exchange data with other phones. But it’s a simpler explanation for the display to just not accurately report what the inside is doing and it to hear a cell tower or a GPS signal for a few hundredths of a second.
What does “location turned off” mean on your phone? It’s a vague term that doesn’t clarify what it’s doing.
There are two aspects to this. The device can use GPS to know where it is. The device can also decide if applications/web-pages are allowed to know where the device is.
Disabling “Location Services”, would prevent applications/web-sites from being able to access the GPS (giving you privacy), but the OS itself will know and will probably do the right thing (maintain clocks, etc).
Digital clocks were a thing long before gps and cellphones. My guess is that it is a simple algorithm that keeps the time.
But I was born nearly a decade before the first moon landing so I am proberly wrong.
Did you turn on airplane mode? If not, it is because your phone contacted the local cell tower. Cell tower signals carry time information. It is separate from data. Phones will automatically switch to the time information sent by the cell tower unless there is other data present to contradict it (definitive GPS location, mobile internet time, etc.)
If the neighboring country’s cell tower isn’t part of your local network, your phone may show a (R)oaming indicator. That is a strong clue that your time will be adjusted to the local zone. I’ve encountered this traveling numerous times.
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