function changeDay(obj)
{
	var form = document.getElementById('form1');
	var year = form.year;
	var month = form.month;
	var day = form.day;

	if(year.selectedIndex!=0 && month.selectedIndex!=0)
	{
		var month_value = month[month.selectedIndex].value;
		if(month_value==1 || month_value==3 || month_value==5 || month_value==7 || month_value==8 || month_value==10 || month_value==12)
		{
			if(day[day.length-1].value==31)
				return;
			else
			{
				for(i=31-day[day.length-1].value;i>0;i--)
				{
					var OptNew = document.createElement('option');
  					OptNew.text = 32-i;
  					OptNew.value = 32-i;
 					try {
    						day.add(OptNew, null); // standards compliant; doesn't work in IE
  					}
  					catch(ex) {
    						day.add(OptNew); // IE only
  					}
				}
			}
		}
		else if(month_value==4 || month_value==6 || month_value==9 || month_value==11)
		{
			if(day[day.length-1].value==30)
				return;
			else if(day[day.length-1].value>30)
			{
				day.remove(day.length-1);
			}
			else if(day[day.length-1].value<30)
			{
				for(i=30-day[day.length-1].value;i>0;i--)
				{
					var OptNew = document.createElement('option');
  					OptNew.text = 31-i;
  					OptNew.value = 31-i;
 					try {
    						day.add(OptNew, null); // standards compliant; doesn't work in IE
  					}
  					catch(ex) {
    						day.add(OptNew); // IE only
  					}
				}
			}
		}
		else if(month_value==2)
		{
			if(year[year.selectedIndex].value % 4 == 0)
			{
				if(day[day.length-1].value==29)
					return;
				else if(day[day.length-1].value>29)
				{
					for(i=day[day.length-1].value-29;i>0;i--)
					{
						day.remove(day.length-1);
					}

				}
				else if(day[day.length-1].value<29)
				{
					for(i=29-day[day.length-1].value;i>0;i--)
					{
						var OptNew = document.createElement('option');
  						OptNew.text = 30-i;
  						OptNew.value = 30-i;
 						try {
    							day.add(OptNew, null); // standards compliant; doesn't work in IE
  						}
  						catch(ex) {
    							day.add(OptNew); // IE only
  						}
					}
				}
			}
			else
			{
				if(day[day.length-1].value==28)
					return;
				else
				{
					for(i=day[day.length-1].value-28;i>0;i--)
					{
						day.remove(day.length-1);
					}
				}
			}
		}
	}	
}