1.在工程文件下面新建文件夹"js",然后向其中添加JavaScript.js新建项，重命名为calendar.js。

2.向calendar.js中写入代码，
复制代码 代码如下:
var cal;
var isFocus=false; //是否为焦点
//function SelectDate(obj,strFormat) //两个参数改为只传一个
function SelectDate(obj)
{
var date = new Date();
var by = date.getFullYear()-80; //最小值 → 80 年前
var ey = date.getFullYear()+20; //最大值 → 20 年后
cal = (cal==null) ? new Calendar(by, ey, 0) : cal; //初始化为中文版，1为英文版
//cal.dateFormatStyle = strFormat; // 默认显示格式为:yyyy-MM-dd ,还可显示 yyyy/MM/dd
cal.show(obj);
}
/**//* 返回日期 */
String.prototype.toDate = function(style){
var y = this.substring(style.indexOf('y'),style.lastIndexOf('y')+1);//年
var m = this.substring(style.indexOf('M'),style.lastIndexOf('M')+1);//月
var d = this.substring(style.indexOf('d'),style.lastIndexOf('d')+1);//日
if(isNaN(y)) y = new Date().getFullYear();
if(isNaN(m)) m = new Date().getMonth();
if(isNaN(d)) d = new Date().getDate();
var dt ;
eval ("dt = new Date('"+ y+"', '"+(m-1)+"','"+ d +"')");
return dt;
}
/**//* 格式化日期 */
Date.prototype.format = function(style){
var o = {
"M+" : this.getMonth() + 1, //month
"d+" : this.getDate(), //day
"h+" : this.getHours(), //hour
"m+" : this.getMinutes(), //minute
"s+" : this.getSeconds(), //second
"w+" : "天一二三四五六".charAt(this.getDay()), //week
"q+" : Math.floor((this.getMonth() + 3) / 3), //quarter
"S" : this.getMilliseconds() //millisecond
}
if(/(y+)/.test(style)){
style = style.replace(RegExp.$1,
(this.getFullYear() + "").substr(4 - RegExp.$1.length));
}
for(var k in o){
if(new RegExp("("+ k +")").test(style)){
style = style.replace(RegExp.$1,
RegExp.$1.length == 1 ? o[k] :
("00" + o[k]).substr(("" + o[k]).length));
}
}
return style;
};

/**//*
* 日历类
* @param beginYear 2009
* @param endYear 2015
* @param lang 0(中文)|1(英语) 可自由扩充
* @param dateFormatStyle "yyyy-MM-dd";
*/
function Calendar(beginYear, endYear, lang, dateFormatStyle){
this.beginYear = 2009;
this.endYear = 2015;
this.lang = 0; //0(中文) | 1(英文)
this.dateFormatStyle = "yyyy-MM-dd";

if (beginYear != null && endYear != null){
this.beginYear = beginYear;
this.endYear = endYear;
}
if (lang != null){
this.lang = lang
}

if (dateFormatStyle != null){
this.dateFormatStyle = dateFormatStyle
}

this.dateControl = null;
this.panel = this.getElementById("calendarPanel");
this.container = this.getElementById("ContainerPanel");
this.form = null;

this.date = new Date();
this.year = this.date.getFullYear();
this.month = this.date.getMonth();


this.colors = {
"cur_word" : "#FFFFFF", //当日日期文字颜色
"cur_bg" : "#83A6F4", //当日日期单元格背影色
"sel_bg" : "#FFCCCC", //已被选择的日期单元格背影色
"sun_word" : "#FF0000", //星期天文字颜色
"sat_word" : "#0000FF", //星期六文字颜色
"td_word_light" : "#333333", //单元格文字颜色
"td_word_dark" : "#CCCCCC", //单元格文字暗色
"td_bg_out" : "#EFEFEF", //单元格背影色
"td_bg_over" : "#FFCC00", //单元格背影色
"tr_word" : "#FFFFFF", //日历头文字颜色
"tr_bg" : "#666666", //日历头背影色
"input_border" : "#CCCCCC", //input控件的边框颜色
"input_bg" : "#EFEFEF" //input控件的背影色
}

this.draw();
this.bindYear();
this.bindMonth();
this.changeSelect();
this.bindData();
}

/**//*
* 日历类属性（语言包，可自由扩展）
*/
Calendar.language ={
"year" : [[""], [""]],
"months" : [["一月","二月","三月","四月","五月","六月","七月","八月","九月","十月","十一月","十二月"],
["JAN","FEB","MAR","APR","MAY","JUN","JUL","AUG","SEP","OCT","NOV","DEC"]
],
"weeks" : [["日","一","二","三","四","五","六"],
["SUN","MON","TUR","WED","THU","FRI","SAT"]
],
"clear" : [["清空"], ["CLS"]],
"today" : [["今天"], ["TODAY"]],
"close" : [["关闭"], ["CLOSE"]]
}

Calendar.prototype.draw = function(){
calendar = this;

var mvAry = [];
mvAry[mvAry.length] = ' <div name="calendarForm" style="margin: 0px;">';
mvAry[mvAry.length] = ' <table width="100%" border="0" cellpadding="0" cellspacing="1">';
mvAry[mvAry.length] = ' <tr>';
mvAry[mvAry.length] = ' <th align="left" width="1%"><input style="border: 1px solid ' + calendar.colors["input_border"] + ';background-color:' + calendar.colors["input_bg"] + ';width:16px;height:20px;" name="prevMonth" type="button" id="prevMonth" value="<" /></th>';
mvAry[mvAry.length] = ' <th align="center"width="98%"><select name="calendarYear" id="calendarYear" style="width:48%;font-size:12px;"></select><select name="calendarMonth" id="calendarMonth" style="font-size:12px;width:48%;"></select></th>';
mvAry[mvAry.length] = ' <th align="right" width="1%"><input style="border: 1px solid ' + calendar.colors["input_border"] + ';background-color:' + calendar.colors["input_bg"] + ';width:16px;height:20px;" name="nextMonth" type="button" id="nextMonth" value=">" /></th>';
mvAry[mvAry.length] = ' </tr>';
mvAry[mvAry.length] = ' </table>';
mvAry[mvAry.length] = ' <table id="calendarTable" width="100%" style="border:0px solid #CCCCCC;background-color:#FFFFFF" border="0" cellpadding="3" cellspacing="1">';
mvAry[mvAry.length] = ' <tr>';
for(var i = 0; i < 7; i++){
mvAry[mvAry.length] = ' <th style="font-weight:normal;background-color:' + calendar.colors["tr_bg"] + ';color:' + calendar.colors["tr_word"] + ';">' + Calendar.language["weeks"][this.lang][i] + '</th>';
}
mvAry[mvAry.length] = ' </tr>';
for(var i = 0; i < 6;i++){
mvAry[mvAry.length] = ' <tr align="center">';
for(var j = 0; j < 7; j++){
if (j == 0){
mvAry[mvAry.length] = ' <td style="cursor:default;color:' + calendar.colors["sun_word"] + ';"></td>';
} else if(j == 6){
mvAry[mvAry.length] = ' <td style="cursor:default;color:' + calendar.colors["sat_word"] + ';"></td>';
} else{
mvAry[mvAry.length] = ' <td style="cursor:default;"></td>';
}
}
mvAry[mvAry.length] = ' </tr>';
}
mvAry[mvAry.length] = ' <tr style="background-color:' + calendar.colors["input_bg"] + ';">';
mvAry[mvAry.length] = ' <th colspan="2"><input name="calendarClear" type="button" id="calendarClear" value="' + Calendar.language["clear"][this.lang] + '" style="border: 1px solid ' + calendar.colors["input_border"] + ';background-color:' + calendar.colors["input_bg"] + ';width:100%;height:20px;font-size:12px;"/></th>';
mvAry[mvAry.length] = ' <th colspan="3"><input name="calendarToday" type="button" id="calendarToday" value="' + Calendar.language["today"][this.lang] + '" style="border: 1px solid ' + calendar.colors["input_border"] + ';background-color:' + calendar.colors["input_bg"] + ';width:100%;height:20px;font-size:12px;"/></th>';
mvAry[mvAry.length] = ' <th colspan="2"><input name="calendarClose" type="button" id="calendarClose" value="' + Calendar.language["close"][this.lang] + '" style="border: 1px solid ' + calendar.colors["input_border"] + ';background-color:' + calendar.colors["input_bg"] + ';width:100%;height:20px;font-size:12px;"/></th>';
mvAry[mvAry.length] = ' </tr>';
mvAry[mvAry.length] = ' </table>';
mvAry[mvAry.length] = ' </div>';
this.panel.innerHTML = mvAry.join("");

var obj = this.getElementById("prevMonth");
obj.onclick = function (){calendar.goPrevMonth(calendar);}
obj.onblur = function (){calendar.onblur();}
this.prevMonth= obj;

obj = this.getElementById("nextMonth");
obj.onclick = function (){calendar.goNextMonth(calendar);}
obj.onblur = function (){calendar.onblur();}
this.nextMonth= obj;


obj = this.getElementById("calendarClear");
obj.onclick = function (){calendar.dateControl.value = "";calendar.hide();}
this.calendarClear = obj;

obj = this.getElementById("calendarClose");
obj.onclick = function (){calendar.hide();}
this.calendarClose = obj;

obj = this.getElementById("calendarYear");
obj.onchange = function (){calendar.update(calendar);}
obj.onblur = function (){calendar.onblur();}
this.calendarYear = obj;

obj = this.getElementById("calendarMonth");
with(obj)
{
onchange = function (){calendar.update(calendar);}
onblur = function (){calendar.onblur();}
}this.calendarMonth = obj;

obj = this.getElementById("calendarToday");
obj.onclick = function (){
var today = new Date();
calendar.date = today;
calendar.year = today.getFullYear();
calendar.month = today.getMonth();
calendar.changeSelect();
calendar.bindData();
calendar.dateControl.value = today.format(calendar.dateFormatStyle);
calendar.hide();
}
this.calendarToday = obj;
}

//年份下拉框绑定数据
Calendar.prototype.bindYear = function(){
var cy = this.calendarYear;
cy.length = 0;
for (var i = this.beginYear; i <= this.endYear; i++){
cy.options[cy.length] = new Option(i + Calendar.language["year"][this.lang], i);
}
}

//月份下拉框绑定数据
Calendar.prototype.bindMonth = function(){
var cm = this.calendarMonth;
cm.length = 0;
for (var i = 0; i < 12; i++){
cm.options[cm.length] = new Option(Calendar.language["months"][this.lang][i], i);
}
}

//向前一月
Calendar.prototype.goPrevMonth = function(e){
if (this.year == this.beginYear && this.month == 0){return;}
this.month--;
if (this.month == -1){
this.year--;
this.month = 11;
}
this.date = new Date(this.year, this.month, 1);
this.changeSelect();
this.bindData();
}

//向后一月
Calendar.prototype.goNextMonth = function(e){
if (this.year == this.endYear && this.month == 11){return;}
this.month++;
if (this.month == 12){
this.year++;
this.month = 0;
}
this.date = new Date(this.year, this.month, 1);
this.changeSelect();
this.bindData();
}

//改变SELECT选中状态
Calendar.prototype.changeSelect = function(){
var cy = this.calendarYear;
var cm = this.calendarMonth;
for (var i= 0; i < cy.length; i++){
if (cy.options[i].value == this.date.getFullYear()){
cy[i].selected = true;
break;
}
}
for (var i= 0; i < cm.length; i++){
if (cm.options[i].value == this.date.getMonth()){
cm[i].selected = true;
break;
}
}
}

//更新年、月
Calendar.prototype.update = function (e){
this.year = e.calendarYear.options[e.calendarYear.selectedIndex].value;
this.month = e.calendarMonth.options[e.calendarMonth.selectedIndex].value;
this.date = new Date(this.year, this.month, 1);
this.changeSelect();
this.bindData();
}

//绑定数据到月视图
Calendar.prototype.bindData = function (){
var calendar = this;
var dateArray = this.getMonthViewArray(this.date.getFullYear(), this.date.getMonth());
var tds = this.getElementById("calendarTable").getElementsByTagName("td");
for(var i = 0; i < tds.length; i++){
tds[i].style.backgroundColor = calendar.colors["td_bg_out"];
tds[i].onclick = function () {return;}
tds[i].onmouseover = function () {return;}
tds[i].onmouseout = function () {return;}
if (i > dateArray.length - 1) break;
tds[i].innerHTML = dateArray[i];
if (dateArray[i] != " "){
tds[i].onclick = function () {
if (calendar.dateControl != null){
calendar.dateControl.value = new Date(calendar.date.getFullYear(),
calendar.date.getMonth(),
this.innerHTML).format(calendar.dateFormatStyle);
}
calendar.hide();
}
tds[i].onmouseover = function () {
this.style.backgroundColor = calendar.colors["td_bg_over"];
}
tds[i].onmouseout = function () {
this.style.backgroundColor = calendar.colors["td_bg_out"];
}
if (new Date().format(calendar.dateFormatStyle) ==
new Date(calendar.date.getFullYear(),
calendar.date.getMonth(),
dateArray[i]).format(calendar.dateFormatStyle)) {
tds[i].style.backgroundColor = calendar.colors["cur_bg"];
tds[i].onmouseover = function () {
this.style.backgroundColor = calendar.colors["td_bg_over"];
}
tds[i].onmouseout = function () {
this.style.backgroundColor = calendar.colors["cur_bg"];
}
}//end if

//设置已被选择的日期单元格背影色
if (calendar.dateControl != null && calendar.dateControl.value == new Date(calendar.date.getFullYear(),
calendar.date.getMonth(),
dateArray[i]).format(calendar.dateFormatStyle)) {
tds[i].style.backgroundColor = calendar.colors["sel_bg"];
tds[i].onmouseover = function () {
this.style.backgroundColor = calendar.colors["td_bg_over"];
}
tds[i].onmouseout = function () {
this.style.backgroundColor = calendar.colors["sel_bg"];
}
}
}
}
}

//根据年、月得到月视图数据(数组形式)
Calendar.prototype.getMonthViewArray = function (y, m) {
var mvArray = [];
var dayOfFirstDay = new Date(y, m, 1).getDay();
var daysOfMonth = new Date(y, m + 1, 0).getDate();
for (var i = 0; i < 42; i++) {
mvArray[i] = " ";
}
for (var i = 0; i < daysOfMonth; i++){
mvArray[i + dayOfFirstDay] = i + 1;
}
return mvArray;
}

//扩展 document.getElementById(id) 多浏览器兼容性 from meizz tree source
Calendar.prototype.getElementById = function(id){
if (typeof(id) != "string" || id == "") return null;
if (document.getElementById) return document.getElementById(id);
if (document.all) return document.all(id);
try {return eval(id);} catch(e){ return null;}
}

//扩展 object.getElementsByTagName(tagName)
Calendar.prototype.getElementsByTagName = function(object, tagName){
if (document.getElementsByTagName) return document.getElementsByTagName(tagName);
if (document.all) return document.all.tags(tagName);
}

//取得HTML控件绝对位置
Calendar.prototype.getAbsPoint = function (e){
var x = e.offsetLeft;
var y = e.offsetTop;
while(e = e.offsetParent){
x += e.offsetLeft;
y += e.offsetTop;
}
return {"x": x, "y": y};
}

//显示日历
Calendar.prototype.show = function (dateObj, popControl) {
if (dateObj == null){
throw new Error("arguments[0] is necessary")
}
this.dateControl = dateObj;

this.date = (dateObj.value.length > 0) ? new Date(dateObj.value.toDate(this.dateFormatStyle)) : new Date() ;//若为空则显示当前月份
this.year = this.date.getFullYear();
this.month = this.date.getMonth();
this.changeSelect();
this.bindData();
if (popControl == null){
popControl = dateObj;
}
var xy = this.getAbsPoint(popControl);
this.panel.style.left = xy.x -25 + "px";
this.panel.style.top = (xy.y + dateObj.offsetHeight) + "px";

this.panel.style.display = "";
this.container.style.display = "";

dateObj.onblur = function(){calendar.onblur();}
this.container.onmouseover = function(){isFocus=true;}
this.container.onmouseout = function(){isFocus=false;}
}

//隐藏日历
Calendar.prototype.hide = function() {
this.panel.style.display = "none";
this.container.style.display = "none";
isFocus=false;
}

//焦点转移时隐藏日历
Calendar.prototype.onblur = function() {
if(!isFocus){this.hide();}
}
document.write('<div id="ContainerPanel" style="display:none;"><div id="calendarPanel" style="position: absolute;display: none;z-index: 9999;');
document.write('background-color: #FFFFFF;border: 1px solid #CCCCCC;width:175px;font-size:12px;margin-left:25px;"></div>');
if(document.all)
{
document.write('<iframe style="position:absolute;z-index:2000;width:expression(this.previousSibling.offsetWidth);');
document.write('height:expression(this.previousSibling.offsetHeight);');
document.write('left:expression(this.previousSibling.offsetLeft);top:expression(this.previousSibling.offsetTop);');
document.write('display:expression(this.previousSibling.style.display);" scrolling="no" frameborder="no"></iframe>');
}
document.write('</div>');

3.保存文件后，即完成了js日历控件的编写。

4.在相应需要日历控件的源处写在head标签下面写
复制代码 代码如下:
<script type="text/javascript" src="/UploadFiles/2021-04-02/calendar.js">
其中，src是你JavaScript的位置

5.所有填写日期的TextBox，加这两个属性：ReadOnly="True" onclick="SelectDate(this)"