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);