Calendar.setup({
              inputField    : "cal-field-1",
              button        : "cal-button-1",
              align         : "Tr",
              ifFormat : "%m/%d/%Y",
              firstDay : 1,
              dateStatusFunc : disablePast,
weekNumbers : false
            }); 

            
            function disablePast(date, y, m, d)
            {
               myDate1 = new Date();
			   myDate2 = new Date(myDate1.getFullYear(), myDate1.getMonth(), myDate1.getDate());
               if (date < myDate2) return true;
            }