iPhone (iOS) · System Info

Set the Date and Time on iPhone

Date & Time settings normally keep your iPhone's clock accurate automatically using your current location and cellular network, but they can also be set manually and switched between 12-hour and 24-hour display.

How to open Date & Time

  1. Open Settings → General → Date & Time.
  2. Confirm 'Set Automatically' is turned on for the clock to update using location and network data.
  3. Toggle '24-Hour Time' on or off to match your preferred clock format.
  4. Turn off 'Set Automatically' only if you specifically need to set the date, time, or time zone manually.

What you should know

  • 'Set Automatically' uses location and network time data to keep the clock and time zone continuously accurate, including during travel.
  • Turning off 'Set Automatically' allows manually choosing a specific time zone, date, and time.
  • The 24-Hour Time toggle switches the whole system, including Lock Screen, Clock, and Calendar, between 12-hour and 24-hour formats.
  • An incorrect time zone can silently shift the accuracy of alarms, calendar events, and message timestamps.

Turning off 'Set Automatically' means the clock and time zone stay fixed until you change them manually, even after traveling to a different time zone.

Why it matters

Accurate date and time settings are foundational to dozens of features working correctly at once — alarms firing on schedule, calendar invitations landing at the right hour, message timestamps making sense, and Screen Time or Focus schedules triggering when expected. Because 'Set Automatically' relies on location and cellular data, disabling Location Services for the system or losing cellular signal in a new time zone can cause the clock to drift out of sync without an obvious warning. This is also one of the first things worth checking when a scheduled reminder, alarm, or calendar event seems to fire at the wrong time.

Best practices

  • Leave 'Set Automatically' turned on for nearly all everyday use, since it reliably adjusts the time zone during travel without any manual intervention.
  • Confirm Location Services is enabled for System Services if the clock seems to be drifting, since time zone detection depends partly on location data.
  • Switch to 24-Hour Time if you regularly work with international teams or schedules where 12-hour AM/PM formatting causes confusion.
  • Double-check the time zone manually right after landing in a new country if you're on airplane mode without cellular service for an extended period.

Common problems and fixes

Clock shows the wrong time zone after landing in a new country
Turn cellular data and Location Services back on so 'Set Automatically' can re-detect the correct time zone, since airplane mode alone can delay the update.
Alarms or calendar events fire an hour off from expected
Check Settings → General → Date & Time to confirm the correct time zone is selected, especially after a recent daylight saving time change.
Manually set time keeps resetting back to automatic detection
This happens because 'Set Automatically' was left on — turn it off explicitly if you need the date and time to stay fixed at a manual value.
24-Hour Time change doesn't seem to apply in a specific app
Most system apps like Clock and Calendar follow this setting immediately, but some third-party apps use their own internal time format preference instead.

Tips and tricks

  • Add a second time zone clock in the Clock app's World Clock tab instead of manually changing your device's time zone to track a different location.
  • Check the small time zone name shown at the top of the Date & Time screen to quickly confirm which zone your iPhone currently thinks it's in.

Frequently asked questions

Why would I ever turn off 'Set Automatically'?

It's mainly useful in rare situations like software testing or specific travel circumstances where automatic time zone detection is unreliable; most users should leave it on.

Does 24-Hour Time change how dates are formatted too?

No, it only affects the clock time format; date formatting (day-first vs. month-first) is controlled separately by the Region setting under Language & Region.

Can my iPhone's clock be wrong even with 'Set Automatically' on?

It's uncommon, but a temporary loss of cellular signal and Location Services together can occasionally delay an automatic time zone update until connectivity is restored.

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