Returns task's current duration in minutes.

def duration(self):
        """ Returns task's current duration in minutes.
            """

        if not self._loaded:
            return 0

        delta = datetime.datetime.now() - self._start_time
        total_secs = (delta.microseconds +
                      (delta.seconds + delta.days * 24 * 3600) *
                      10 ** 6) / 10 ** 6

        return max(0, int(round(total_secs / 60.0)))