Calendar displays month incorrectly.

My iPad (64 GB) calendar has a bug. When moving from one month to the next it will not display the month correctly. It will show the next months days, but identifies it as the month prior until the display is moved half way into the following month. Interestingly the first five month identifiers show as bolded, but from June on they are not bolded.

I have rebooted the iPad three times, software is current, iCloud backup performed. Any fix suggestions appreciated.