title: Youtube API video duration format
body: <pre><code>{
   "kind": "youtube#videoListResponse",
   "etag": "\"XlbeM5oNbUofJuiuGi6IkumnZR8/ny1S4th-ku477VARrY_U4tIqcTw\"",
   "items": [
    {
  
     "id": "9bZkp7q19f0",
     "kind": "youtube#video",
     "etag": "\"XlbeM5oNbUofJuiuGi6IkumnZR8/HN8ILnw-DBXyCcTsc7JG0z51BGg\"",
     "contentDetails": {
      "duration": "PT4M13S",
      "dimension": "2d",
      "definition": "hd",
      "caption": "false",
      "licensedContent": true,
      "regionRestriction": {
       "blocked": [
        "DE"
       ]
      }
     }
    }
   ]
  }
  </code></pre>
  
  <p>Youtube API v3 provides its video durations in this format <code>"duration": "PT4M13S"</code> Is this a standard time format?  I'm trying to get a user friendly format using Objective-C. I would like to know if this is a Objective-C DateTime class supported format. If not what are those P,T, charactors stands for?</p>