function get_num_days( year, month ) {
var days;
if( month == 2 ){
<!-- is this a leap year? -->
if( year % 4 != 0 ){
days = 28;
} else if( year % 400 == 0 ){
days = 29;
} else if( year % 100 == 0 ){
days = 28;
} else{
days = 29;
}
} else if( month == 4 || month == 6 || month == 9 || month == 11 ){
days = 30;
} else{
days = 31;
}
return days;
}
   

function update_numeric_select( s, limit ) {

var current = s.selectedIndex;

var len = s.length;
for( i = len - 1; i >= 0; i-- ){
  s.options[i] = null;
}
for( i = 0; i < limit; i++ ) {
  var option = new Option( i+1, i+1 );
  s.options[i] = option;
}
if( limit < current + 1 ) {
  s.selectedIndex = 0;
} else {
  s.selectedIndex = current;
}
return;
}