Date.prototype.Format = function (fmt) { //author: meizz

    var o = {

        "M+": this.getMonth() + 1, //月份

        "d+": this.getDate(), //日

        "h+": this.getHours(), //小时

        "m+": this.getMinutes(), //分

        "s+": this.getSeconds(), //秒

        "q+": Math.floor((this.getMonth() + 3) / 3), //季度

        "S": this.getMilliseconds() //毫秒

    };

    if (/(y+)/.test(fmt)) fmt = fmt.replace(RegExp.$1, (this.getFullYear() + "").substr(4 - RegExp.$1.length));

    for (var k in o)

    if (new RegExp("(" + k + ")").test(fmt)) fmt = fmt.replace(RegExp.$1, (RegExp.$1.length == 1) ? (o[k]) : (("00" + o[k]).substr(("" + o[k]).length)));

    return fmt;

}

	function daysJian(){

	  var date = new Date('2006-7-1 8:9:4.18');//获取当前时间

	  date.setDate(date.getDate()-1);//设置天数 -1 天

	   var time = date.Format("yyyy-MM-dd");

	   return time;

	}

console.log(daysJian());

console.log("=====================")
console.log(new Date(1234567897789).Format("yyyy-MM-dd hh:mm:ss"))