def age
      list = txns
      list.empty? ? 0 : (Time.now - list.min_by(&:date).date) / (60 * 60)
    end
def age
      list = txns
      list.empty? ? 0 : (Time.now - list.min_by(&:date).date) / (60 * 60)
    end
Age of wallet in hours.