js配合My97datepicker给日期添加天数

<input name="ctl00$ContentPlaceHolder1$txtTimeStart" type="text" value="2013-09-11" maxlength="50" id="txtTimeStart" class="Wdate" onclick="WdatePicker({dateFmt:'yyyy-MM-dd',skin:'whyGreen',isShowClear:false,onpicking:onpicking})" readonly="true" style="width:150px;" />

Date.prototype.format = function(format) {
var o =
{
"M+": this.getMonth() + 1, //month
"d+": this.getDate(), //day
"h+": this.getHours(), //hour
"m+": this.getMinutes(), //minute
"s+": this.getSeconds(), //second
"q+": Math.floor((this.getMonth() + 3) / 3), //quarter
"S": this.getMilliseconds() //millisecond
}
if (/(y+)/.test(format))
format = format.replace(RegExp.$1, (this.getFullYear() + "").substr(4 - RegExp.$1.length));
for (var k in o)
if (new RegExp("(" + k + ")").test(format))
format = format.replace(RegExp.$1, RegExp.$1.length == 1 ? o[k] : ("00" + o[k]).substr(("" + o[k]).length));
return format;
}

function onpicking(dp) {
var ddlType = document.getElementById('<%=ddlPType.ClientID %>');
var txtPName = document.getElementById('<%=txtPName.ClientID %>');
var text = ddlType.options[ddlType.selectedIndex].text;
var value = ddlType.options[ddlType.selectedIndex].value;
if (value == "2") {
var newDate = dp.cal.getNewDateStr();
var dt = new Date(newDate);
var newDate2 = dt.getFullYear() + '-' + dt.getMonth() + '-' + dt.getDay() + 6;

txtPName.value = newDate + '~' + DateAdd(dt, 6).format('yyyy-MM-dd') + '' + text;
} else {
var newDate = dp.cal.getNewDateStr();
txtPName.value = newDate + text;
}
}

function DateAdd(sdate, days) {
var a = new Date(sdate);
a = a.valueOf();
a = a + days * 24 * 60 * 60 * 1000;
a = new Date(a);
return a;
}

var strdates="2011-10-21";

var strdays=365;

var d = strdates.replace(/-/g,'/');
var now = new Date(d);
var values = AddDays(now,strdays);

var strt= values.format("yyyy-MM-dd");

alert(strt)

function AddDays(date,value)
{
return new Date(Date.parse(date) + (86400000 * value));
}