title: Grep log file greater than time stamp
body: <p>I have a unix log file(application.log), that has logs with timestamp at the starting. I need to search for a pattern "sent" in this log file  greater than time 2014-03-20 14:05:54. </p>
  
  <pre><code>2014-03-20 14:05:54,038 [NfxAgent....
  2014-03-20 14:05:54,164 [NfxAgent....
  2014-03-20 14:05:54,298 [NfxAgent....
  2014-03-20 14:05:54,414 [NfxAgent....
  2014-03-20 14:05:54,787 [NfxAgent....
  </code></pre>