Try force closing the calendar app. From the home screen, double-tap the home button, locate Calendars in the list at the bottom, tap an hold it until it wiggles, tap to close it, tap the home button again. Open your calendar again and see if it's working properly now.
If you're syncing your calendar with iCloud, you could try going to Settings>iCloud, turn Calendars to Off, choose Delete from My iPad when prompted, then after a minute or so turn Calendars back to On, which will sync your iCloud calendars back to yoru phone. Then try opening your calendar again.
I thought it was working. I did as you recommended and the empty calendar began to refill with content from my Mac and iPhone. However, when March was almost complete it collapsed and won't revive. Puzzling. Pip