function catcalc(cal) {
		
		var date = cal.date;
        var time = date.getTime()
        // use the _other_ field
        var field = document.getElementById("katalog-bsd");
        if (field == cal.params.inputField) {
            field = document.getElementById("katalog-vnd");
            time -= Date.WEEK; // substract one week
        } else {
            time += Date.WEEK; // add one week
            time += Date.WEEK; // add one week
        }
        var date2 = new Date(time);
        field.value = date2.print("%d.%m.%Y");
        
        jahr_vnd = document.getElementById("katalog-vnd").value; jahr_vnd = jahr_vnd.substr(6,4);
		jahr_bsd = document.getElementById("katalog-bsd").value; jahr_bsd = jahr_bsd.substr(6,4);
        
        monat_vnd = document.getElementById("katalog-vnd").value; monat_vnd = monat_vnd.substr(3,2);
		monat_bsd = document.getElementById("katalog-bsd").value; monat_bsd = monat_bsd.substr(3,2);
        
        tag_vnd = document.getElementById("katalog-vnd").value; tag_vnd = tag_vnd.substr(0,2);
		tag_bsd = document.getElementById("katalog-bsd").value; tag_bsd = tag_bsd.substr(0,2);
        
       	document.getElementById("vnd").value = new Date(jahr_vnd,monat_vnd-1,tag_vnd,12,0,0).getTime()/1000;
		document.getElementById("bsd").value = new Date(jahr_bsd,monat_bsd-1,tag_bsd,12,0,0).getTime()/1000;
        
  }
  
function setstartdatum() {
	
	var cal_startdatum = new Date();
	var cal_in7Tagen = new Date( cal_startdatum.getTime() + ( 3  * 24 * 60 * 60 * 1000) );  
	document.getElementById("katalog-vnd").value = cal_in7Tagen.print("%d.%m.%Y");
	var cal_in21Tagen = new Date( cal_startdatum.getTime() + ( 30  * 24 * 60 * 60 * 1000) );
	document.getElementById("katalog-bsd").value = cal_in21Tagen.print("%d.%m.%Y");
	
	jahr_vnd = document.getElementById("katalog-vnd").value; jahr_vnd = jahr_vnd.substr(6,4);
	jahr_bsd = document.getElementById("katalog-bsd").value; jahr_bsd = jahr_bsd.substr(6,4);
    
    monat_vnd = document.getElementById("katalog-vnd").value; monat_vnd = monat_vnd.substr(3,2);
	monat_bsd = document.getElementById("katalog-bsd").value; monat_bsd = monat_bsd.substr(3,2);
    
    tag_vnd = document.getElementById("katalog-vnd").value; tag_vnd = tag_vnd.substr(0,2);
	tag_bsd = document.getElementById("katalog-bsd").value; tag_bsd = tag_bsd.substr(0,2);
    
   	document.getElementById("vnd").value = new Date(jahr_vnd,monat_vnd-1,tag_vnd,12,0,0).getTime()/1000;
	document.getElementById("bsd").value = new Date(jahr_bsd,monat_bsd-1,tag_bsd,12,0,0).getTime()/1000;
	
}