$.validator.addMethod('daterange', function(value, element, arg) {
     // Same as above

     var startDate = Date.parse(arg[0]),
         endDate = Date.parse(arg[1]),
         enteredDate = Date.parse(value);
     // Same as below

 }, $.validator.format("Please specify a date between {0} and {1}."))

$.validator.addMethod('daterange', function(value, element) {
    if (this.optional(element)) {
        return true;
    }

    var startDate = Date.parse('2010-11-29'),
        endDate = Date.parse('2010-12-15'),
        enteredDate = Date.parse(value);

    if (isNan(enteredDate)) {
        return false;
    }

    return ((startDate <= enteredDate) && (enteredDate <= endDate));
});

if(isNaN(enteredDate)) return false;

    return ((startDate <= enteredDate) && (enteredDate <= endDate));
}, "Please specify a date between 2010-11-29 and 2010-12-15");

$.validator.addMethod('dateRange', function (value, element, parameterValue) {
        if (this.optional(element) && !value) {
            return true;
        }
        var dateFormat = $(element).datepicker('option', 'dateFormat');
        try {
            var startDate = $.datepicker.parseDate(dateFormat, parameterValue[0]).getTime();
            var endDate = $.datepicker.parseDate(dateFormat, parameterValue[1]).getTime();
            var enteredDate = $.datepicker.parseDate(dateFormat, value).getTime();
            return (startDate <= enteredDate) && (enteredDate <= endDate);
        } catch (error) {
            return true;
        }
    });

$.validator.addMethod('daterange', function(value, element, arg) {
    if (this.optional(element) && !value) {
        return true;
    }

    var startDate = Date.parse(arg[0]),
        endDate = Date.parse(arg[1]),
        enteredDate = Date.parse(value);

    if (isNaN(enteredDate)) {
        return false;
    }

    return ( (isNaN(startDate) || (startDate <= enteredDate)) &&
             (isNaN(endDate) || (enteredDate <= endDate)));


   }, $.validator.format("Please specify a date between {0} and {1}."));

$("#some_date_input").rules("add",{daterange:['01/31/2001','01/31/2020']});