// add a method. calls one built-in method, too.
jQuery.validator.addMethod("optdate", function(value, element) {
return jQuery.validator.methods['date'].call(
this,value,element
)||value==("0000/00/00");
}, "Please enter a valid date."
);
// connect it to a css class
jQuery.validator.addClassRules({
optdate : { optdate : true }
});