           false
       end
     end
-    def is_valid?(_), do: false
+
+    def is_valid?(_),
+      do: false
   end
 
   defimpl String.Chars, for: DateTuple do

  """
  @spec normalise_year(String.t | integer) :: integer | :nil
  def normalise_year(year)
  def normalise_year(""), do: :nil
  def normalise_year(year) when is_binary(year) do
    normalise_year String.to_integer(year)
  end
  def normalise_year(year) when year < 100 do
    normalise_year(year + 2000, :past_only)
  end
  def normalise_year(year), do: year
  def normalise_year(year, :past_only) do
    current_year = DateTime.utc_now.year
    cond do

        normalise_month month_integer
    end
  end

  def normalise_month(month) when month > 0 and month < 13,
    do: month
  def normalise_month(_),
    do: :nil


  @doc """
