title: MongoDB Return the count of documents for each day for the last one month
body: <p>I have a collection with documents updating everyday. Can someone provide me some suggestion for returning the count of the documents added on every day for the last one month.
  I am having a field with created time stamp as shown here ..
  "createdTimestamp" : ISODate("2014-03-19T19:25:23.351Z")</p>