JSON对象中存在的日期分组

Question

所以我有很多从Facebook API返回的JSON对象，其中一个如下所示。

{
  "_id": ObjectId("503ded9103c4b72fef12aa2f"),
  "from": {
    "category": "Company",
    "name": "Fortis Healthcare",
    "id": "165708715950"
  },
  "pid": "165708715950_377424172280794",
  "like_count": NumberInt(0),
  "can_remove": false,
  "created_time": "2012-04-02T09:58:48+0000",
  "message": "For academic info check out http:\/\/www.fortishospitals.com\/about-fortis-hospitals\/academic-initiatives.html",
  "id": "165708715950_377424172280794_4682416",
  "user_likes": false
}

我需要做的是，我需要对属于他们月份的所有日期进行分组，并从这些对象中提取“message”参数。如何对这几个月的日期进行分组？