js获取当前时间前一周时间前一个月时间

//获取系统当前时间
var nowdate = new Date();
var y = nowdate.getFullYear();
var m = nowdate.getMonth()+1;
var d = nowdate.getDate();
var formatnowdate = y+'-'+m+'-'+d;
$("#enddate").datebox("setValue",formatnowdate);
//获取系统前一周的时间
var oneweekdate = new Date(nowdate-7*24*3600*1000);
var y = oneweekdate.getFullYear();
var m = oneweekdate.getMonth()+1;
var d = oneweekdate.getDate();
var formatwdate = y+'-'+m+'-'+d;
$("#fdate").datebox("setValue",formatwdate);
//获取系统前一个月的时间
nowdate.setMonth(nowdate.getMonth()-1);
var y = nowdate.getFullYear();
var m = nowdate.getMonth()+1;
var d = nowdate.getDate();
var formatwdate = y+'-'+m+'-'+d;
$("#fdate").datebox("setValue",formatwdate);