/* Kan het meegegeven element wel of niet tonen */
        
         function showElement(span, show) 
         {
             element1 = document.getElementById(span);
             if (show == 'true') {
                 element1.style.display = 'inline';
             }
             else {
                 element1.style.display = 'none';
             }
         }

	function prevent_previous_page_return() 
	{
		window.history.forward();
        	}

	/* Veranderd de stijl van een textbox */

	/* Veranderd de stijl van een element */

         function changeTextbox(element) {
             element.style.color = "#0f245a";
         }

        /* Bereken de leeftijd en toon een fieldset als de leeftijd onder de 18 is */
    
        var startyear = "1950";
        var endyear = "2010";
        var dat = new Date();

        var curday = dat.getDate();
        var curmon = dat.getMonth()+1;
        var curyear = dat.getFullYear();

        function checkleapyear(datea)
        {
	        if(datea.getYear()%4 == 0)
	        {
		        if(datea.getYear()% 10 != 0)
		        {
			        return true;
		        }
		        else
		        {
			        if(datea.getYear()% 400 == 0)
				        return true;
			        else
				        return false;
		        }
	        }
        return false;
        }
        
        function DaysInMonth(Y, M) {
            with (new Date(Y, M, 1, 12)) {
                setDate(0);
                return getDate();
            }
        }
        
        function datediff(date1, date2) {
            var y1 = date1.getFullYear(), m1 = date1.getMonth(), d1 = date1.getDate(),
	         y2 = date2.getFullYear(), m2 = date2.getMonth(), d2 = date2.getDate();

            if (d1 < d2) {
                m1--;
                d1 += DaysInMonth(y2, m2);
            }
            if (m1 < m2) {
                y1--;
                m1 += 12;
            }
            return [y1 - y2, m1 - m2, d1 - d2];
        }

        function calage(ddlDay, ddlMonth, ddlYear) {

            var calday = ddlDay.value;
            var calmon = ddlMonth.value
            var calyear = ddlYear.value;
	        
	        var curd = new Date(curyear,curmon-1,curday);
	        var cald = new Date(calyear,calmon-1,calday);
    		
	        var diff =  Date.UTC(curyear,curmon,curday,0,0,0) - Date.UTC(calyear,calmon,calday,0,0,0);

	        var dife = datediff(curd,cald);
	        var monleft = (dife[0]*12)+dife[1];
	        var secleft = diff/1000/60;
	        var hrsleft = secleft/60;
	        var daysleft = hrsleft/24;
	        var as = parseInt(calyear)+dife[0]+1;
	        var diff =  Date.UTC(as,calmon,calday,0,0,0) - Date.UTC(curyear,curmon,curday,0,0,0);
	        var datee = diff / 1000 / 60 / 60 / 24;

	        if (dife[0] < 18) {
	            showElement("fieldsetBetaling", 'true');
	        }
	        else {
	            showElement("fieldsetBetaling", 'false');
	        }
        }