DATEDIF FUNCTION

Koi16 

1) DATEDIF is a weird function. For many years, it wasn't officially documented by Microsoft. It is now, but with a warning that the result is not always accurate: DATEDIF function 

2) Date calculations involving the last days of a month are always problematic:

It's reasonable to say that from February 20, 2023 to March 20, 2023 is exactly 1 month, since both dates are on the same day of the month.

And from February 20, 2023 to March 21, 2023 is 1 month and 1 day.

Following the same reasoning, from February 28, 2023 to March 28, 2023 is 1 month.

From February 28, 2023 to March 29, 2023 is one day more, so 1 month and 1 day.

From February 28, 2023 to March 30, 2023 is 1 month and 2 days.

From February 28, 2023 to March 31, 2023 is 1 month and 3 days.

But February 28 and March 31 are both the last day of their month, so it is also reasonable to say that it is exactly 1 month and 0 days.

There is no one single solution that will satisfy everybody...