Just come across this problem, and quickly managed to work out how to get around it.
1. You have an ‘all-day’ or birthday event (from Address Book) configured for 1st April 2013, and the relevant calendar is selected for display.
1. Select Month View
1. Navigate to March 2013 – Crash!
**Update: On 28th January 2013, Apple released iOS 6.1 which appears to fix the problem. Make sure you have upgraded!**
1. Disable the calendar containing the event
2. Use an alternate view from Month view
3. Delete the offending event or birthday.
If iCal/Calendar crashes due to the bug, just reload, and you’ll either be back at Today, or one month either side of March 2013. Switch view (for example to Week View), and you’ll be able to navigate back to March 2013 without crashing.
If you have Facebook enabled in Settings, you may need to switch off contact and calendar sync, or remove the Facebook account. Check your contacts for any with a birthday on 1st April, and delete the birthday if you find one. Then you should be able to view March 2013 in Mpnth View without crashing.
**if you are interested in Calendar alternatives for iPhone & iPad, consider [signing up at Calendar-Apps.com](http://calendar-apps.com) for in-depth reviews of apps that help you get organised.**