One way:

=SUM(COUNTIF(A:A,{"12/09/05","12/10/05","12/11/05"}))

In article ,
Jim wrote:

I would like to know how I can write a countif to count the number of times
dates are entered into a column and add those dates together. For example I
would like to count the number of times that 12/9/05, 12/10/05, and 12/11/05
appear in a column that shows multiple dates. Thanks for the help.

12/9/05
12/10/05
12/13/05
12/22/05
12/10/05
12/30/05
12/9/05
12/10/05
12/13/05
12/22/05
12/10/05
12/30/05
12/9/05
12/10/05
12/13/05
12/22/05
12/10/05
12/30/05