function catcalc(cal) {
		var date = cal.date;
        var time = date.getTime()
        // use the _other_ field
        var field = document.getElementById("tt_ruecktermin");
        if (field == cal.params.inputField) {
            field = document.getElementById("tt_termin");
            time -= Date.WEEK; // substract one week
        } else {
            time += Date.WEEK; // add one week
        }
        var date2 = new Date(time);
        field.value = date2.print("%d.%m.%Y");
    }

function setstartdatum() {
	
	var cal_startdatum = new Date();
	
	var cal_in7Tagen = new Date( cal_startdatum.getTime() + ( 3  * 24 * 60 * 60 * 1000) );  
	document.getElementById("tt_termin").value = cal_in7Tagen.print("%d.%m.%Y");
	var cal_in21Tagen = new Date( cal_startdatum.getTime() + ( 30  * 24 * 60 * 60 * 1000) );
	document.getElementById("tt_ruecktermin").value = cal_in21Tagen.print("%d.%m.%Y");
	
	jahr_termin = document.getElementById("tt_termin").value; jahr_termin = jahr_termin.substr(6,4);
	jahr_ruecktermin = document.getElementById("tt_ruecktermin").value; jahr_ruecktermin = jahr_ruecktermin.substr(6,4);
    
    monat_termin = document.getElementById("tt_termin").value; monat_termin = monat_termin.substr(3,2);
	monat_ruecktermin = document.getElementById("tt_ruecktermin").value; monat_ruecktermin = monat_ruecktermin.substr(3,2);
    
    tag_termin = document.getElementById("tt_termin").value; tag_termin = tag_termin.substr(0,2);
	tag_ruecktermin = document.getElementById("tt_ruecktermin").value; tag_ruecktermin = tag_ruecktermin.substr(0,2);
    
   	document.getElementById("termin").value = new Date(jahr_termin,monat_termin-1,tag_termin,12,0,0).getTime()/1000;
	document.getElementById("ruecktermin").value = new Date(jahr_ruecktermin,monat_ruecktermin-1,tag_ruecktermin,12,0,0).getTime()/1000;
	
}