The iPhone displays the current date and time of day at the top of the screen on all of the phone's application menu pages. The date and time are also relevant for the Calendar application and the Clock application, and especially the Alarm feature. The iPhone date and time can be set to automatically update with daylight saving's time and changes in geography, or users can manually adjust the date and time settings. Changing the date and time on the iPhone is a simple task and takes just a few moments.
Click on "Settings," then "General," then "Date & Time."
Toggle the "24-hour Time" meter on or off depending on your preference. By default, the iPhone displays the time in 12-hour format.
Toggle the "Set Automatically" meter to on for the iPhone to automatically adjust the time and date depending on your time zone. When the iPhone is set to update automatically, it uses available cell phone networks to determine your location and adjusts the time accordingly. However, when you travel to some locations that lack cell phone networks, you will have to manually adjust the time and date.
Toggle the "Set Automatically" meter to off to manually adjust the time and date. This will bring up another panel of settings. Select "Time Zone" to change the time zone by entering a city name, and select "Date and Time" to manually enter this data.
It is wise to occasionally check your phone's date and time settings for accuracy, especially when you have been travelling in and out of different time zones. Occasionally the iPhone will fail to change the date and time when entering a new time zone even when the phone is connected to an active cell phone network. Before manually changing the date and time, turn the phone off and then on again to see if it changes on its own, as sometimes this helps.