docs: def last_session_date(self):
          """Return date/time for start of last session data."""
          try:
              date = self.intervals[1]['ts']
          except KeyError:
              return None
          date_f = datetime.strptime(date, '%Y-%m-%dT%H:%M:%S.%fZ')
          now = time.time()
          offset = datetime.fromtimestamp(now) - datetime.utcfromtimestamp(now)
          return date_f + offset