<html> <head> <title>Date substraction</title> </head> <body> <script language="JavaScript" type="text/javascript"> <!-- var myVar = prompt("Enter a future date: ") var user_date = Date.parse(myVar); var today_date = new Date(); var diff_date = user_date - today_date; document.write(diff_date); //--> </script> </body> </html>