title: Symfony2 Doctrine MySQL UTC_TIMESTAMP()
body: <p>I am trying to convert plain MySQL query to Doctrine query builder in Symfony2. 
  I had a following part of SELECT query calculating different between the UTC timestamp in rcv.rtcdatetime field and current UTC:</p>
  
  <pre><code>TIMESTAMPDIFF(SECOND, rcv.rtcdatetime, UTC_TIMESTAMP()) AS utcdiff
  </code></pre>
  
  <p>Apparently the UTC_TIMESTAMP() function is not available in Doctrine. I managed to find CURRENT_TIMESTAMP() function in Doctrine but I cannot find what value is supposed to be returned by that function. Is it the local server time or UTC timestamp? I tested it on several servers and still not sure.</p>