Count if value has more than four duplicates

[haan0054]

Range A1:A500 contain dates and many of them are duplicates. I'd like to count al dates which have more than four duplicates. For instance if 01-01-2010 would appear more than four times in the range it should be counted.

I tried to get it work in an array formula with frequency but to no avail.

please help.

Thanks