If you own an iPad, be sure to update to iOS 4.2 for an improved MobileMe Calendar experience including push updates for calendar event changes.
Here's how to update your iPad to iOS 4.2:
1. Make sure you're running iTunes version 10.1 or later
2. Connect your iPad to iTunes on your computer
3. Select it in the Devices list
4. Click "Check for Update"
Please note: If you were already using the new MobileMe Calendar on your iPad and have manually configured your calendar account, please follow these instructions after updating to iOS 4.2.
via apple.com

