var months = new Array();
'January', 'February', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'October', 'November', 'December'
months[0] = 31;
months[1] = 28;
months[2] = 31;
months[3] = 30;
months[4] = 31;
months[5] = 30;
months[6] = 31;
months[7] = 31;
months[8] = 30;
months[9] = 31;
months[10] = 30;
months[11] = 31;

/*months['January'] = 31;
months['February'] = 28;
months['March'] = 31;
months['April'] = 30;
months['May'] = 31;
months['June'] = 30;
months['July'] = 31;
months['August'] = 31;
months['September'] = 30;
months['October'] = 31;
months['November'] = 30;
months['December'] = 31;
*/
function calculateDays(idday, idmonth, idyear)
{
    var dayObject = document.getElementById(idday);
    
    var monthObject = document.getElementById(idmonth);
    var yearObject  = document.getElementById(idyear);

    var maxDay = 31;
    if (monthObject.selectedIndex != 1) {        
        maxDay = months[monthObject.value];        
    } else {
  	   var year = parseInt(yearObject.value);
  	   if (year % 4 == 0) {
  	 	  maxDay = 29;
  	   } else {
  	      maxDay = 28;
       }       
    }
    /*
    if (monthObject.value != 'February') {        
        maxDay = months[monthObject.value];
    } else {
  	   var year = parseInt(yearObject.value);
  	   if (year % 4 == 0) {
  	 	  maxDay = 29;
  	   } else {
  	      maxDay = 28;
       }
    }*/
  	var select = dayObject.selectedIndex;
	while (dayObject.firstChild) {
		dayObject.removeChild(dayObject.firstChild);
	}
	for (var i = 1; i <= maxDay; i++) {
		option = document.createElement("option");
		option.value = i;
		option.innerHTML = i;
		dayObject.appendChild(option);
	}
	if (select < maxDay) {
		dayObject.selectedIndex = select;
	}
}