/*   Script inspired by "True Date Selector"
     Created by: Lee Hinder, lee.hinder@ntlworld.com 
     
     Tested with Windows IE 6.0
     Tested with Linux Opera 7.21, Mozilla 1.3, Konqueror 3.1.0
     
*/

function daysInFebruary (year){
  // February has 28 days unless the year is divisible by four,
  // and if it is the turn of the century then the century year
  // must also be divisible by 400 when it has 29 days
  return (((year % 4 == 0) && ( (!(year % 100 == 0)) || (year % 400 == 0))) ? 29 : 28 );
}

//function for returning how many days there are in a month including leap years
function DaysInMonth(WhichMonth, WhichYear)
{
  var DaysInMonth = 31;
  if (WhichMonth == "4" || WhichMonth == "6" || WhichMonth == "9" || WhichMonth == "11")
    DaysInMonth = 30;
  if (WhichMonth == "2")
    DaysInMonth = daysInFebruary( WhichYear );
  return DaysInMonth;
}

//function to change the available days in a months
function ChangeOptionDays(formObj, prefix)
{
  var DaysObject = eval("formObj." + prefix + "day");
  var MonthObject = eval("formObj." + prefix + "month");
  var YearObject = eval("formObj." + prefix + "year");

  if (DaysObject.selectedIndex && DaysObject.options)
    { // The DOM2 standard way
    // alert("The DOM2 standard way");
    var DaySelIdx = DaysObject.selectedIndex;
    var Month = parseInt(MonthObject.options[MonthObject.selectedIndex].value);
    var Year = parseInt(YearObject.options[YearObject.selectedIndex].value);
    }
  else if (DaysObject.selectedIndex && DaysObject[DaysObject.selectedIndex])
    { // The legacy MRBS way
    // alert("The legacy MRBS way");
    var DaySelIdx = DaysObject.selectedIndex;
    var Month = parseInt(MonthObject[MonthObject.selectedIndex].value);
    var Year = parseInt(YearObject[YearObject.selectedIndex].value);
    }
  else if (DaysObject.value)
    { // Opera 6 stores the selectedIndex in property 'value'.
    // alert("The Opera 6 way");
    var DaySelIdx = parseInt(DaysObject.value);
    var Month = parseInt(MonthObject.options[MonthObject.value].value);
    var Year = parseInt(YearObject.options[YearObject.value].value);
    }

  // alert("Day="+(DaySelIdx+1)+" Month="+Month+" Year="+Year);

  var DaysForThisSelection = DaysInMonth(Month, Year);
  var CurrentDaysInSelection = DaysObject.length;
  if (CurrentDaysInSelection > DaysForThisSelection)
  {
    for (i=0; i<(CurrentDaysInSelection-DaysForThisSelection); i++)
    {
      DaysObject.options[DaysObject.options.length - 1] = null
    }
  }
  if (DaysForThisSelection > CurrentDaysInSelection)
  {
    for (i=0; i<DaysForThisSelection; i++)
    {
      DaysObject.options[i] = new Option(eval(i + 1));
    }
  }
  if (DaysObject.selectedIndex < 0) DaysObject.selectedIndex = 0;
  if (DaySelIdx >= DaysForThisSelection)
    DaysObject.selectedIndex = DaysForThisSelection-1;
  else
    DaysObject.selectedIndex = DaySelIdx;
}