This will work, make sure to array enter it (CTRL+SHIFT+ENTER):

=SUM(--(FREQUENCY(IF(MONTH(C1:C1000)=8,MATCH(C1:C1000,C1: C1000,0)),ROW(INDIRECT("1:"&ROWS(C1:C1000))))0))

--
Regards,
Dave


" wrote:

Hi Everyone,

I need a little help on this...

Each row on colum C has a date in date format
The same date can appear more then once within the column
not all days within a month will necessarayl appear, so for August,
even tought it has 31 days, there might be 500 entries, but only
spanned across 10 different days.

Example of colum C:

Date
July 22, 2006
July 23, 2006
August 01, 2006
August 01, 2006
August 03, 2006
August 03, 2006
August 03, 2006
August 05, 2006
August 06, 2006

I need to count how many unique days within the month of august are
within this column, the example above has 4 days within august. How
would I go about doing this with a single formula? I have other ways of
calculating this but creating a table with all the days and then using
a countif, but that would be bukly and slow for something that has to
keep at least 1 year's worth of data.