title: Converting MySQL datetime to ElasticSearch strict_date_optional_time
body: <p>While trying to insert MySQL to ElasticSearch, I'm getting the following error: <code>mapper_parsing_exception: failed to parse [updated_time]</code></p>
  
  <p>The <code>updated_time</code> I'm trying to push is <code>2017-01-23 17:41:27</code></p>
  
  <p>The mapping is defined as: </p>
  
  <pre><code>"updated_time": {
       "type": "date",
       "format": "strict_date_optional_time||epoch_millis"
   }
  </code></pre>
  
  <p>Oddly, when sending such a datetime from Logstash, ElasticSearch is ok with it. But when sending from the official PHP library it fails on this. </p>
  
  <p>It looks like a pretty strict datetime object that comes directly from MySQL. Do I need to convert it? </p>