If memory serves, I believe I've seen this formula suggested by others. It
should ignore blank cells. Change range as needed.

=SUMPRODUCT(--(A1:A6<""),1/COUNTIF(A1:A6,A1:A6&""))

If there are no empty cells in your data you could shorten it to
=SUMPRODUCT(1/COUNTIF(A1:A5,A1:A5))

"bob" wrote:

I have a column with the following dates:

11/23/05
11/23/05
11/23/05
11/25/05
11/25/05
11/28/05
12/1/05
12/1/05
12/1/05

I want a formula that will tell me how many unique dates there are in the
column. Can anyone help?

thanks,
Bob