function checkDates(date1Str, date2Str) { var date1 = new Date(date1Str.substring(6,10), date1Str.substring(0,2)-1, date1Str.substring(3,5)); var date2 = new Date(date2Str.substring(6,10), date2Str.substring(0,2)-1, date2Str.substring(3,5)); if (date1.valueOf() > date2.valueOf()) alert('Date Start cannot be greater than Date End'); }With the assumption that the dates will always be in mm/dd/yyyy format. HTH