I have column from a software export that contains dates, yet some of them are in a convoluted format, no matter what i do i can't unify the whole column into date format, so i'm now trying to do a near as count of occurrences in the column, say how many occurences in each month of each year,

so i started with the formula

=SUMPRODUCT(('Export 02-08-2012'!M:M>=A2)*('Export 02-08-2012'!M:M<=B2))

and then tried

=SUMPRODUCT(IFISDATE(('Export 02-08-2012'!M:M>=A1)*('Export 02-08-2012'!M:M<=B1)))

the first bringing back the #VALUE! error, the second the #NAME? error

any suggestions folks?