You need to install the “Exchange calendar patch”. Easiest way to install it is by launching Safari from the iPhone and go to: http://support.apple.com/kb/ts3398
You need to shutdown the iPhone and then turn it back on after you install this patch (this step seems to make a difference on the devices I tested).
(Note: actual name of the patch is: iOS 4.0: Exchange Mail, Contacts, or Calendars may not sync after update)
1. For the initial setup of the Exchange email profile use the – Mail Days to Sync – settings based on the screenshot below – that is 2 Weeks. Mail Folders to Push setting is based on user’s preference.
(Note: pay close attention to the name you use for this profile – I’m using the name “Exchange”. You’ll need to remember this name to identify the correct calendar.)
2. Go to Settings, tap on Mail, Contacts, Calendars, tap on Fetch New Data and make sure the settings reflect the screenshot below.
(Note: this will consume a bit more battery power, but I’ve found this to make a big difference when it comes to synchronizing with our Exchange server)
3. Stay in Mail, Contacts, Calendars and scroll all the way to the bottom of this screen and tap on Default Calendar.
The following are very important steps!!!
• Under the Exchange heading (see note in step 1), make sure that only ONE calendar shows and that there is a checkmark next to it. If there is more than one calendar showing, then you’ll need to work with the user to remove/delete the additional calendar(s).• To remove any additional calendar(s) showing, you’ll have to use the user’s Outlook client to remove them, and you’ll need to wait a few minutes and repeat step 1 all over again. (Please be very careful, otherwise you may end up deleting user’s data, and obviously make sure the user is fine with removing those calendars!)
(Note: in my tests, it seems that the calendar sync issue lies with either duplicate calendars or, at times, corrupt recurring calendar events – the latter takes longer to fix and until it gets fixed the iPhone will not sync calendars properly. I’ve not encountered issues with corrupt recurring calendar events yet)
4. Now, head back to the home screen on the iPhone and tap on the calendar application. Next, tap on the Calendars button (upper left hand corner button), and the screen should resemble something similar to the screenshot on the right. The Exchange heading (see note in step 1) must show only ONE calendar, and it should have a checkmark next to it – so it displays.
(Note: the initial sync process does take a while, so make sure you let the user know that the Exchange calendar will take up to an hour to fully sync.)