Date compare in javascript ?

var returnDate = "";
        function convertMonthText(DTime) {
            var monthtext = ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sept', 'Oct', 'Nov', 'Dec'];
            var DateFormat = DTime.getDate();           
            if (DateFormat < 10) {
                returnDate = "0" + DTime.getDate() + "/" + monthtext[DTime.getMonth()] + "/" + DTime.getYear();
            }
            else {
                returnDate = DTime.getDate() + "/" + monthtext[DTime.getMonth()] + "/" + DTime.getYear();
            }           
        }

        function CompareDateToToday() {
            var dateChoosed = document.getElementById('TextBox1').value;
            var someDate = new Date();
            var numberOfDaysToAdd = 7;
            someDate.setDate(someDate.getDate() + numberOfDaysToAdd);

            convertMonthText(someDate);
            if (dateChoosed < returnDate) {
                alert('The date for responses should be at least a week after start date.')
                document.getElementById('TextBox1').value = "";
            }
        }

//---------- Support all browse below code

function convertMonthTextToNumeric(DTime) {
            var ReturnDateFormatedValue = "";
            var _Array = DTime.split('/');
            if (_Array.length > 2) {
                var _Month = "";
                if (_Array[1] == "Jan")
                    _Month = "01";
                else if (_Array[1] == "Feb")
                    _Month = "02";
                else if (_Array[1] == "Mar")
                    _Month = "03";
                else if (_Array[1] == "Apr")
                    _Month = "04";
                else if (_Array[1] == "May")
                    _Month = "05";
                else if (_Array[1] == "Jun")
                    _Month = "06";
                else if (_Array[1] == "Jul")
                    _Month = "07";
                else if (_Array[1] == "Aug")
                    _Month = "08";
                else if (_Array[1] == "Sep")
                    _Month = "09";
                else if (_Array[1] == "Oct")
                    _Month = "10";
                else if (_Array[1] == "Nov")
                    _Month = "11";
                else if (_Array[1] == "Dec")
                    _Month = "12";
                else
                    _Month = "01";

                ReturnDateFormatedValue = _Array[2] + "/" + _Month + "/" + _Array[0];
            }
            return ReturnDateFormatedValue;
        }



        function CheckDateValidation() {
            var getStartDateFormated = "";
            var getEndtDateFormated = "";
            getStartDateFormated = convertMonthTextToNumeric(document.getElementById('txtStartDate').value);
            getEndtDateFormated = convertMonthTextToNumeric(document.getElementById('txtEndDate').value);

            getStartDateFormated = new Date(getStartDateFormated);
            getEndtDateFormated = new Date(getEndtDateFormated);

            var numberOfDaysToAdd = 7;
            getStartDateFormated.setDate(getStartDateFormated.getDate() + numberOfDaysToAdd);

            if (getEndtDateFormated < getStartDateFormated) {
                alert('The date for responses should be at least a week after start date.')
                document.getElementById('txtEndDate').value = "";
            }
        }