title: date format and elasticsearch 1.7
body: <p>I am trying to store unixtimestamp as a value to a field in Elasticsearch Index. The version I am using is 1.7.3.
  While indexing the data mapping for the field is :-</p>
  
  <pre><code>             {"type":"date","format":"dateOptionalTime"}
  </code></pre>
  
  <p>the data is stored properly but when I try to query the particular field for date value I get parse exception.
  query used is :- </p>
  
  <pre><code>             {"query":{"term":{"contentPublishedTime":1447764265}}}
  </code></pre>
  
  <p>Error prompted :- </p>
  
  <pre><code>             IllegalArgumentException[Invalid format: "1447764265" is malformed at "5"]
  </code></pre>