How can I made an AddressBook synchronized with my Iphone addressbook?

I have to made an app with an AddressBook, different by the internal iphone AddressBook, but I need to take informations f开发者_如何学运维rom it (and I can do that), and I need to know (if exists) the internal AdressBook last modify date, so i could sync my app's addressbook with the internal one only if it occours, HOW I CAN DO THAT?? THANK YOU AND SORRY FOR MY BAD ENGLISH!

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Are you storing Contacts to your app locally ? if Not then You don't have to Sync.

ABAddressBook is centralized DB of contacts. so every time your app open you are using ABAddressBook to load the contacts it should get the all latest contacts.