iPhone: About General Settings
Screen brightness affects battery life. Dim the screen to extend the time before you need to recharge iPhone. Or use Auto-Brightness, which is designed to conserve battery life.
Adjust the screen brightness
Choose Brightness and drag the slider.
Set whether iPhone adjusts screen brightness automatically
Choose Brightness and turn Auto-Brightness on or off. If Auto-Brightness is on, iPhone adjusts the screen brightness for current light conditions.
You see a wallpaper background picture when you unlock iPhone or when you've on a call with someone you don't have a photo for.
Choose Wallpaper and choose a picture.
Date and Time
These settings apply to the time shown in the status bar at the top of the screen, world clocks, and calendar.
Set whether iPhone shows 24-hour time or 12-hour time
Choose General > Date & Time and turn 24-Hour Time on or off.
Set whether iPhone sets the date and time automatically
Choose General > Date & Time and turn Set Automatically on or off.
If iPhone is set to update the time automatically, it gets the correct time over the cell network, and updates it for the time zone you're in.
Set the time manually
Choose General > Date & Time and turn Set Automatically off. Then enter a time zone, date, and time.
Turn on Calendar time zone support
Choose General > Date & Time and turn Time Zone Support on. When Time Zone Support is on, Calendar displays event dates and times in the time zone set for your calendars. When Time Zone Support is off, Calendar displays events in the time zone of your current location.
Locking iPhone turns off the display. Nothing happens if you touch the screen. You can still receive calls and text messages, an you can adjust the volume and use the mic button on the iPhone Stereo headset when listening to music or on a call.
Set the amount of time before iPhone locks
Choose General > Auto-Lock and choose a time.
By default, iPhone doesn't require you to enter a passcode to unlock it.
Set a passcode
Choose General > Passcode Lock and enter a 4-digit passcode. iPhone then requires you to enter the passcode to unlock it.
Turn passcode lock off or change the passcode
Choose General > Passcode Lock and tap Turn Passcode Off or Change Passcode, then enter the current passcode.