If I assume that (say) you have no valid date prior to 1/1/1960, then searching for dates >1/1/1960 omits any blank dates.
Putting the search criterion '=' into the date field also finds any that are blank.
If you want to add it as a necessary condition to your original search then just add it to your search criteria as an 'Omit' request.
You could add it as a request using 'Constrain Found Set' but I think that feature came out after version 6.
Thanks, the equal sign dropped out of my tiny head this morning ... Jay
And OMIT works just fine, too.