iso 8601 timestamp in swift

func isoTimestamp() -> String
{
   let dateFormatter = NSDateFormatter()
   // dateFormatter.timeZone = NSTimeZone.localTimeZone()
   // C# "yyyy-MM-ddTHH:mm:ss.fffZ"
   dateFormatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss.SSS'Z'"
   return dateFormatter.stringFromDate(NSDate())
}