mui 结束时间不能大于开始时间

var $timeStart   = document.getElementById('timeStart');
var $timeEnd     = document.getElementById('timeEnd');

$timeStart.addEventListener('tap', function() {
	var optionsJson = this.getAttribute('data-options') || '{}';
	var options = JSON.parse(optionsJson);
	var id = this.getAttribute('id');
	var picker = new mui.DtPicker(options);
	picker.show(function(rs) {
		$timeStart.value = rs.text;
		picker.dispose();
	});
	$Validate.remove("timeStart_活动时间开始 必须填写.");
}, false);

$timeEnd.addEventListener('tap', function() {
	var timestart = $timeStart.value;
	var picker = new mui.DtPicker({
	    type: "datetime",
	    beginDate: new Date(timestart),
	    endDate: new Date(2021, 12, 31 , 23, 59),
	    labels: ['年', '月', '日', '时', '分'],
	})
	picker.show(function(rs) {
		$timeEnd.value = rs.text;
		picker.dispose();
	});
	$Validate.remove("timeEnd_活动时间结束 必须填写.");
}, false);