Validate the date format

Validate the date format

            function checkdate(input) {
                var validformat = /^\d{2}\/\d{2}\/\d{4}$/;  //Basic check for format validity
                var returnval = false;
                if (!validformat.test(input.value))
                    alert("Invalid Date Format. Please correct and submit again.");
                else { //Detailed check for valid date ranges
                    var monthfield = input.value.split("/")[0];
                    var dayfield = input.value.split("/")[1];
                    var yearfield = input.value.split("/")[2];
                    var dayobj = new Date(yearfield, monthfield - 1, dayfield);
                    if ((dayobj.getMonth() + 1 != monthfield) || (dayobj.getDate() != dayfield) || (dayobj.getFullYear() != yearfield))
                        alert("Invalid Day, Month, or Year range detected. Please correct and submit again.");
                    else
                        returnval = true;
                }
                if (returnval == false) input.select();
                return returnval;
            }