def range

      now = Time.now

      [ (Time.parse(@history.first['seen_at']) rescue now),
        (Time.parse(@history.last['seen_at']) rescue now) ]
    end
def range

      now = Time.now

      [ (Time.parse(@history.first['seen_at']) rescue now),
        (Time.parse(@history.last['seen_at']) rescue now) ]
    end
Returns an array [ most recent date, oldest date ] (Time instances).