Q: I have two old iPhones and just got a new iPhone 4. Is there a way to get both of the old iPhones’ information on to my new one?
A: Unfortunately, there is no way to completely aggregate information from two separate iPhones onto a single target device. Some information such as media content and calendar and contact information can be combined by merging into a single iTunes library and personal information application and then syncing it onto the new iPhone from there. Our guide on Copying Content from your iPod to your Computer has more information on how to do this with regard to media content. You can merge calendar and contact info onto a single computer simply by syncing both of your devices with the same iTunes library; iTunes will offer you the option to merge your information into whatever desktop app you’re using, such as Outlook or iCal and Address Book.
For other information such as system preferences and application data, you’re basically out of luck unless those applications provide their own method for doing this. iTunes backs up each of your iPhones separately, so you can choose to restore your new iPhone 4 from either one of those backups, but not both. You will therefore need to basically choose with of the two old iPhones has the most relevant information and then use that backup to restore to your new iPhone 4. The process for doing this is relatively straightforward: Simply connect the old iPhone to whichever computer you normally sync it with and iTunes should make a backup; you can check this by going into your iTunes Preferences and taking a look at the “Devices” tab.
When you connect your new iPhone 4 to that same computer, iTunes will prompt you to either set it up as a new device, or restore from an existing backup. Simply select the appropriate backup and all of your settings from the old iPhone will be restored, including your sync settings with iTunes.
Once you’ve restored this backup onto your iPhone 4, you can then add whatever supported content is available on the second iPhone, such as merging calendars and contacts or copying additional media content into iTunes. Once copied back, this content will simply sync over to the new iPhone 4 the next time you connect it in the same way as any other content in your iTunes library.