How can i have greaterThan and equalTo in validation for the same string?

Question

I am using validate.js to check the dates. I want end date to be equal to or greater than start date. how do I check this using jquery? Can I have two rules to the above jquery?

$("#edate").rules("add", {
    greaterThan: "#sdate",
    messages: {
        greaterThan: "end date must be greater than start date"
    }
});