title: Remove old records in mongodb
body: <p>I have records of the following type in Mongo DB. </p>
  
  <pre><code>{
      "_id" : ObjectId("50217d8874ebb0e4e52cc07d"),   
      "timestamp" : "8/7/12 1:41:36 PM Pacific Daylight Time",
      "_ts" : ISODate("2012-08-07T20:41:44.119Z")
  }
  </code></pre>
  
  <p>How do I remove old records? I have tried something like <code>db.offlineLogs.remove({timestamp: {$lt:new Date("2012, 8, 3")}});</code>, but it doesn't work. </p>