(new Date()).toString("Y年m月d日 H時i分s秒bミリ")にした。

たぶんないとおもいます....

Date.prototype.toString = function(format){
    var now = new Date();
    year = (function (){ var y = now.getYear();   if(y < 2000){ y  += 1900; }; return y; })();
    month= (function (){ var m = now.getMonth()+1;if(m  < 10){ m = "0" + m; }; return m; })();
    day  = (function (){ var d = now.getDate();   if(d < 10) { d = "0" + d; }; return d; })();
    hour = (function (){ var h = now.getHours();  if(h < 10) { h = "0" + h; }; return h; })();
    min  = (function (){ var m = now.getMinutes();if(m < 10) { m = "0" + m; }; return m; })();
    sec  = (function (){ var s = now.getSeconds();if(s < 10) { s = "0" + s; }; return s; })();
    mec  = (function (){ var m = now.getTime() % 1000;                         return m; })();

    if(format){
      return format
            .replace(/Y/g,year)
            .replace(/m/g,month)
            .replace(/d/g,day)
            .replace(/H/g,hour)
            .replace(/i/g,min)
            .replace(/s/g,sec)
            .replace(/b/g,mec);
    }else{
      return year + "年" + month + "月" + day + "日 " +
             hour + "時" + min + "分"   + sec + "." + mec + "秒";
    }
  };

うまく動くといいですね。