(User manual)

Chapter 8 Settings 109
Set date, time, and telephone number formats: Choose General > International >
Region Format, and choose your region.
Resetting iPhone
Reset all settings: Choose General > Reset and tap Reset All Settings.
All your preferences and settings are reset. Information, such as your contacts and
calendars, and media, such as your songs and videos, are not deleted.
Erase all content and settings: Connect iPhone to your computer or a power adapter.
Choose General > Reset and tap “Erase All Content and Settings.”
This feature resets all settings to their defaults and removes all your information and
media on your iPhone by overwriting the data stored on iPhone.
Important: You can’t use iPhone while data is being overwritten. This can take one to
two hours or more, depending on the storage capacity of your iPhone.
Reset the keyboard dictionary: Choose General > Reset and tap Reset Keyboard
Dictionary.
You add words to the keyboard dictionary by rejecting words iPhone suggests as you
type. Tap a word to reject the correction and add the word to the keyboard dictionary.
Resetting the keyboard dictionary erases all words you’ve added.
Reset network settings: Choose General > Reset and tap Reset Network Settings.
When you reset network settings, your list of previously used networks and your VPN
settings are removed. Wi-Fi is turned off and then back on, disconnecting you from any
network you’re on. The Wi-Fi and “Ask to Join Networks” settings are left turned on.
Reset the Home screen layout: Choose General > Reset and tap Reset Home Screen
Layout.
Reset the location warnings: Choose General > Reset and tap Reset Location
Warnings.
Location warnings are the requests made by applications (such as Camera and Maps)
to use Location Services with those applications. iPhone stops presenting the warning
for an application the second time you tap OK. Tap Reset Location Warnings to resume
the warnings.
Mail, Contacts, Calendars
Use Mail, Contacts, Calendars settings to set up and customize accounts for iPhone:
Microsoft Exchange 
MobileMe 
Google email 
Yahoo! Mail 
AOL 