title: Mongo/Mongoose: Why does this query fail?
body: <p>I'm trying to find documents in mongoDB that are older than a specific amount of time. 
  Here is an example of a document in my database that should be returned,</p>
  
  <pre><code>{
      "_id" : ObjectId("5cc07ea943eeba155840b62f"),
      "name" : "test3",
      "value" : 3,
      "created_at" : {
          "$date" : 1556119209477
      },
      "updatedAt" : {
          "$date" : 1556119209477
      },
      "__v" : 0
  }
  </code></pre>
  
  <p>Here is the query I have so far....</p>
  
  <pre><code>Item.find({"created_at":{$lt:new Date(Date.now() - keys.anAmountOfMilliseconds)}}, (err, foundItems) =&gt; {
  </code></pre>
  
  <p>When run like this, the following error is returned: { CastError: Cast to date failed for value "Invalid Date" at path "created_at" for model "items"</p>
  
  <p>When searching for documents using, createdAt or "createdAt", the query returns with nothing....</p>