When I sync the outlook calendar to my iphone, one of two things happens. 1. If I put an all day event in outlook, it syncs to the iphone a day earlier (both otlook & iphone are on same date & time). 2. If I alter that rror on the iphone, then sync to outlook, the outlook date then runs across two days from 1am to 1am. Any thoughts? This has only started recently & I've had my iphone for over a year. Thanks

Make sure time-zone is the same for both iPhone and the computer.

On iPhone setting > Mail,Contacts,Calendars setting > Time Zone Support, make sure you are choosing the city where you are in.

Otherwise, make sure you have updated the iTunes to 7.5 or later.

Update to iTunes 7.5 or later to resolve this issue. If you're not able to update, continue reading for other options to resolve the issue.
Each Outlook calendar event has an internal property known as "Message Class." When some Outlook plug-ins are installed (such as Live Search Maps), the setting for the Message Class property can change from its default of "IPM.Appointment" to something else. iPhone and iPod touch are only able sync calendar events with the Message Class set to "IPM.Appointment," therefore any calendar events created after installing certain Outlook plugins may no longer sync.
To verify this, examine the property of the Calendar event items for MS Outlook and see if the Message Class shows something other than "IPM.Appointment" in any of the calendar events. To view the Message Class property for your Outlook Calendar events, add the Message Class field as one of the columns in the Current View using these steps:

1. Open Outlook Calendar on the computer.
2. Choose View > Current View > Events.
3. For Windows Vista, choose View > Current View > Customize Current View.
   For Windows XP, choose View > Arrange By > Current View > Customize Current View.
4. Click the Fields button and choose All Appointment fields from the pop-up menu in the "Select available fields from" section.
5. In the "Available Fields" column, select "Message Class" and click the Add button.
6. Click OK.
7. Click OK.

1. Uninstall any Outlook plugins such as Live Search Maps or other plugins which change the default Message Class "IPM.Appointment" to some other value. Once the plugins have been removed, verify if those calendar events revert back to the Message Class of "IPM.Appointment" so that you can sync the calendar data to iPhone/iPod touch. If you are able to sync, try adding the plugins back one at a time and verify that you are still able to sync.
2. If removing the Outlook plugins does not change the Message Class value for the calendar events, manually change the Message Class value of those calendar events to "IPM.Appointment." For more information on Message Class and how to change the Message Class fields/value, refer to Microsoft's KB article 201087 How to update existing items in an Outlook folder to use a new custom form