Alan,
I believe you want to assess whether you have duplicate dates in a range of interest, not a count by individual dates.
You can do the assessment by means of a formula and/or identify duplicate dates by using conditional formatting.
Diagnostic formula that you can use is:
=COUNT(A2:A100)-IF(LEN(A2:A100),SUMPRODUCT(1/COUNTIF(A2:A100,A2:A100)))
The number that this formula produces indicates how many date duplicates you have in the range A2:A100, where the first date entry is in A2.
In order to identify duplicates:
Select A2:A100 [ the date range of interest ];
Activate Format|Conditional Formatting;
Choose Formula Is for Condition 1;
Enter in the formula box:
=COUNTIF($A$2:$A$100,A2)>1 [ do not freeze A2, that is, no $-sign wrt A2 ]
Activate Format;
Select a color on the Patterns tab.
Click OK, OK.
Aladin