mootools-1.2.2.1-more.js

 getWeek: function(){
  var day = (new Date(this.get('year'), 0, 1)).get('date');//应该为get('day');
  return Math.round((this.get('dayofyear') + (day > 3 ? day - 4 : day + 3)) / 7);
 },

mootools-1.2.3.1-more.js

 getWeek: function(){
  return (this.get('dayofyear')  / 7).ceil();
 },

这个完全错