1. Which email service is your calendar associated with? iCloud, Gmail, Yahoo, Outllook.com, etc?
2. Go to Settings-Mail, Contacts, Calendars and then scroll down to the "Calendars" section and make sure the settings are to your liking.
3. Now in the Calendar app (I'm assuming you're using the native calendar app), either select the "+" sign in the upper right corner or tap and hold on a time slot in the calendar itself to add a new entry.
4. If that does not work, reboot your device and try again.
5. If that fails, go to Settings-General-Reset and then select "Reset All Settings".
6. If that fails, connect your device to iTunes, create a backup, and then restore it as a new device.
10-27-2013 10:41 AM