Regardless of how they are formatted, Excel dates are stored as the
number of days since the beginning of 1900. Provided that the entry is
an Excel date or can be coerced into an Excel date, the formula should work.

Data QC is often the biggest portion of data analysis.

Jerry

Steve Wylie wrote:

Yeah, that's the trouble. The dates have not been inputted consistently.
There are many false entries where people have put "16 Dec" and no year (it
should all be dd.mm.yy) or just "age 42" or rubbish like that. The analysis
program I use just ignores all that, whereas Excel throws up an error.

And I suspect your formula doesn't like the years in two-digit format
either...

Thanks, but I did it using the analysis program in the end. Shame tho.

Steve