jQuery Forum

You need a custom method and a required-dependency, roughly something like this:
$.validator.addMethod("customDate", function(value, element) {
var day = $("#day").val(), month = ...;
return valid(day + month + year);
});
function dateRequired() {
return $("#day")[0].selectedIndex > 0 &&
$("#month")[0].selectedIndex > 0 && $("#year").val().length;
}
...
rules: {
day: { required: dateRequired, customDate: true },
month: { required: dateRequired, customDate: true },
year: { required: dateRequired, customDate: true }
}
The dateRequired function assumes that the first option is the blank one.
The customDate method needs to be completed, the existing date methods
may help as reference.
Jörn