Maand = new Array(
"0", "jan",
"1", "feb",
"2", "mar",
"3", "apr",
"4", "mei",
"5", "jun",
"6", "jul",
"7", "aug",
"8", "sep",
"9", "okt",
"10", "nov",
"11", "dec");

function PrintListBox(QuestionName, MySize, KeuzenLijst)
{
  document.write("<select NAME=\"" + QuestionName + "\" SIZE=\"1\" style=\"width:");
  document.write(MySize + "\"  OnClick=\"Caculate()\">");

  for(var KeuzenCounter = 0; KeuzenCounter<KeuzenLijst.length; KeuzenCounter+=2)
  {
    document.write("<option VALUE=\"" + KeuzenLijst[KeuzenCounter] + "\">");
    document.write(KeuzenLijst[KeuzenCounter+1] + "</option>");
  }
  document.write("</select>");
}

function CreateArray(start, eind)
{
  MyArray = new Array(2*(eind-start+1));
   
  for(var i=0; i<eind-start+1 ; i++)
  {
    MyArray[2*i] = "" + (start + i);
    MyArray[2*i+1] = "" + (start + i);
  }
  
  return MyArray;
}

function Caculate()
{
	MyDate = new Date(
        document.Uitgeteld.InJaar.value,
        document.Uitgeteld.InMaand.value,
        document.Uitgeteld.InDag.value);

	// de zwangerschap duurt 40 weken = 40*7*24*3600000 ms
	MyDate.setTime(24192000000 + MyDate.getTime());

  document.Uitgeteld.UitJaar.value = MyDate.getYear();
  document.Uitgeteld.UitMaand.value = MyDate.getMonth();
  document.Uitgeteld.UitDag.value = MyDate.getDate();
}

// draw table
document.write("<TABLE width=260 border=1 bgcolor=5687C5>");
document.write("<TR><TD bgcolor=#C8D4EC><center><b>Bereken hier je uitgetelde datum</b>");

document.write("<FORM NAME=\"Uitgeteld\">");
document.write("Eerste dag van de laatste menstruatie<br>");
PrintListBox("InDag", 40, CreateArray(1,31));
PrintListBox("InMaand", 50, Maand);
PrintListBox("InJaar", 60, CreateArray(2007,2012));

document.write("<br><br>Uitgetelde datum<br>");
PrintListBox("UitDag", 40, CreateArray(1,31));
PrintListBox("UitMaand", 50, Maand);
PrintListBox("UitJaar", 60, CreateArray(2007,2012));

document.write("</FORM></TD></TR></TABLE>");

// get date and calculate
Nu = new Date();

document.Uitgeteld.InJaar.value = Nu.getYear();
document.Uitgeteld.InMaand.value = Nu.getMonth();
document.Uitgeteld.InDag.value = Nu.getDate();

Caculate();