How to Change an iPhone Clock Display
The iPhone is somewhat customisable and allows users to make slight interface changes such as assigning an image to your home screen or rearranging the order of widgets. You can also change the clock display on your iPhone. You can choose from two options when displaying the iPhone clock.
You can display the clock as a 12-hour clock or a 24-hour clock.
Turn on and unlock your iPhone. Hold down the "Power" button until you see an Apple logo. Once the firmware has loaded, swipe your finger across the "Slide to unlock" bar at the bottom of the touch screen.
Tap "Settings." This is a grey or silver icon that is located on your "Home" screen. A list of options and settings appears.
Tap "General." A list of general settings appears.
Scroll down the screen and tap "Date & Time." The "Date & Time" options screen displays.
Tap the "ON/OFF" switch next to 24-hour time to either enable or disable 24-hour time. The clock display will immediately change. You can view the new clock display at the top of the phone.