Does your phone change time zone by itself when you travel?

The two settings that make it automatic

On iPhone, Apple's troubleshooting steps start with a connection to the internet and the latest software. Then open Settings, tap General, then Date & Time, and turn on Set Automatically (in recent versions, Set Time Zone Automatically). Second, go to Settings, Privacy & Security, Location Services, scroll down to System Services and turn on Setting Time Zone. Apple says this lets the device use its current location to work out the correct time zone.

On Android, Google's Clock help gives the route: open Clock, tap More and then Settings, tap Change date and time, and turn on Automatic date and time. Under Time zone, turn on Automatic time zone. Google adds that if Use location is turned off, your device location will not be used to detect the time zone.

Why the clock can be wrong for a while after landing

Apple's own wording explains most cases: the time zone is set automatically, but if Location Services is off or you do not have service, you change it manually. Straight off a plane, a phone that was in airplane mode may have neither a network nor a fresh location yet, and keeps showing home time until it gets one.

Getting online usually settles it. Apple's checklist begins with making sure the device is connected to the internet, and says that if a message appears saying updated time zone information is available, you should restart the device and any paired Apple Watch.

With a travel eSIM installed at home, the phone connects as soon as you switch the data line on after landing. A data-only plan like Snoozim's starts counting at that first connection in the destination, not before.

Alarms: check the one that matters

This is where people get caught. Apple's documentation does not spell out how Clock alarms behave when you change time zone, and reports from iPhone users on Apple's own forums disagree about whether an alarm moves with you. With an early flight or a meeting, do not find out the hard way.

The simple routine: after the phone shows local time, open the alarm and check that it says the local time you want to wake up. If you set it before the flight, set a test alarm a couple of minutes ahead and watch it ring. On Android, the Clock app has an Automatic home clock option that adds a clock with your home time while you are in another time zone, which makes it easier to see which time you are looking at.

Flight times are local at each airport

Airline bookings and boarding passes give the departure time in the local time of the departure airport and the arrival time in the local time of the arrival airport. A mark such as +1 next to an arrival means it lands the next day.

That is why a flight can appear to land before it took off, or to last far longer than it does. Do not work out the duration from the two clock times; the booking normally shows it separately. And when you plan a transfer, an airport pickup or a hotel check-in, use the arrival time as printed, in the destination's time, not converted to home.

Calendar events across time zones

Apple's Calendar shows events in the time zone of your current location. That is helpful for local plans and confusing for calls with home, so Apple offers two tools. When you create an event, tap its start and end times and then Time Zone to schedule it in another zone. And in Settings, Apps, Calendar, Time Zone Override keeps the whole calendar in one time zone of your choice, even if you travel.

Apple notes that events created before you turn Time Zone Override on show in the new time zone but also display the original one. It also points out that the override only changes the time shown in Calendar, not the phone's clock.

Setting it by hand, and when you cannot

If the clock stays wrong, Apple's advice is to turn off Set Automatically, tap Time Zone and enter a city with the time zone you need. On Android, turn off the automatic option under Time zone and choose yours from the list. Remember to turn automatic back on later, or the next country will catch you out.

If the setting is greyed out on an iPhone, Apple says a Screen Time passcode or a corporate profile with device restrictions can be the reason, which is common on work phones. Our guide to using a travel eSIM on a work phone covers what those restrictions usually mean.