function toggle_tz(tz) {
	
	if (tz == undefined || tz == "" || tz == false) tz = 'nachmittag';
	Effect.toggle('pplan_' + tz + 's','blind', { duration: 0.8 });
	Effect.toggle('tr_' + tz + '_on','appear', { duration: 0.2 });
	Effect.toggle('tr_' + tz + '_off','appear', { duration: 0.2 });

	if (document.getElementById('pplan_' + tz + 's').style.display == "none") {
		var toggle_item = 'pplan_' + tz + 's';
		window.setTimeout("document.getElementById("+toggle_item+").style.display = 'block';", 700);
	}

}