Days between two dates in excel

Question

I'm trying to calculate the number of days between two dates in Excel and am running into a weird issue.

I know that I should be able to just subtract the dates, but it's not behaving.

Right now I have 3 dates, using a custom format of yyyy-mm-dd:

2007-06-08, 2007-06-20, 2008-06-20, (A1, B1, C1)

I then try to calculate the difference between these.

=C1-A1 ("2008-06-20"-"2007-06-08") returns 378, formatted as a general cell, as expected.

=C1-B1 (2008-06-20"-"2007-06-20") returns "1900-12-31" formatted with the custom yyyy-mm-dd format.

I'm confused. As far as I can tell both of these calculations take in equivalent data, formatted the same, but produce very different results.

Anyone have any insight?

Answer 1

As highlighted by Ron Rosenfeld above, the issue was with cell formatting. Excel was formatting the two columns differently. When formatted as general the results were both as expected.