Inconsistency with equal formulas

I have all the cells in a structured table flagged as inconcistent. All the forumulas contain

=DATEDIF(birthdays[@[01.08.2010]]; age[[#Kopfzeilen];[01.08.2010]]; "d") / 365.2425

where the only thing varying is the date (01.08.2010 thrue 01.08.2024) of the header cell. Is this normal?