DATEDIF -- date formatting problem (I think)

hello friends.

I have two columns with dates and want to compute years (or months) between them.

I THINK excel is not recognizing my dates as dates and is returning a #NUM error when I try to subtract.

BUT I can't seem to reformat the dates (because excel says they're formatted as dates).

ideas? what am I missing??

THANK YOU SO MUCH. I feel like a moron.

I'm laughing. sorry I'm a moron.

THANK YOU Tsjallie. please feel free to mock.