SOURCE

$(function(){
    var myDate = new Date();
    myDate = myDate.DateAdd("m",1).Format("YYYY-MM-DD HH:mm");
   // myDate = myDate.DateAdd("n",1);
    alert(myDate);
});


Date.prototype.DateAdd = function(strInterval, Number) {   
    var dtTmp = this;  
    switch (strInterval) {   
        case 's' :return new Date(Date.parse(dtTmp) + (1000 * Number));  
        case 'n' :return new Date(Date.parse(dtTmp) + (60000 * Number));  
        case 'h' :return new Date(Date.parse(dtTmp) + (3600000 * Number));  
        case 'd' :return new Date(Date.parse(dtTmp) + (86400000 * Number));  
        case 'w' :return new Date(Date.parse(dtTmp) + ((86400000 * 7) * Number));  
        case 'q' :return new Date(dtTmp.getFullYear(), (dtTmp.getMonth()) + Number*3, dtTmp.getDate(), dtTmp.getHours(), dtTmp.getMinutes(), dtTmp.getSeconds());  
        case 'm' :return new Date(dtTmp.getFullYear(), (dtTmp.getMonth()) + Number, dtTmp.getDate(), dtTmp.getHours(), dtTmp.getMinutes(), dtTmp.getSeconds());  
        case 'y' :return new Date((dtTmp.getFullYear() + Number), dtTmp.getMonth(), dtTmp.getDate(), dtTmp.getHours(), dtTmp.getMinutes(), dtTmp.getSeconds());  
    }  
} 

//---------------------------------------------------  
// 日期格式化  
// 格式 YYYY/yyyy/YY/yy 表示年份  
// MM/M 月份  
// W/w 星期  
// dd/DD/d/D 日期  
// hh/HH/h/H 时间  
// mm/m 分钟  
// ss/SS/s/S 秒  
//---------------------------------------------------  
Date.prototype.Format = function(formatStr)   
{   
    var str = formatStr;   
    var Week = ['日','一','二','三','四','五','六'];  
  
    str=str.replace(/yyyy|YYYY/,this.getFullYear());   
    str=str.replace(/yy|YY/,(this.getYear() % 100)>9?(this.getYear() % 100).toString():'0' + (this.getYear() % 100));   
  
    str=str.replace(/MM/,this.getMonth()>9?this.getMonth().toString():'0' + this.getMonth());   
    str=str.replace(/M/g,this.getMonth());   
  
    str=str.replace(/w|W/g,Week[this.getDay()]);   
  
    str=str.replace(/dd|DD/,this.getDate()>9?this.getDate().toString():'0' + this.getDate());   
    str=str.replace(/d|D/g,this.getDate());   
  
    str=str.replace(/hh|HH/,this.getHours()>9?this.getHours().toString():'0' + this.getHours());   
    str=str.replace(/h|H/g,this.getHours());   
    str=str.replace(/mm/,this.getMinutes()>9?this.getMinutes().toString():'0' + this.getMinutes());   
    str=str.replace(/m/g,this.getMinutes());   
  
    str=str.replace(/ss|SS/,this.getSeconds()>9?this.getSeconds().toString():'0' + this.getSeconds());   
    str=str.replace(/s|S/g,this.getSeconds());   
  
    return str;   
}