   end
 
   @doc false
-  @doc since: "1.5.0"
   def add_day_fraction_to_iso_days({days, {parts, ppd}}, add, ppd) do
     normalize_iso_days(days, parts + add, ppd)
   end

    do: precision_for_unit(div(number, 10), precision + 1)

  @doc false
  @doc since: "1.5.0"
  def date_to_iso8601(year, month, day, format \\ :extended) do
    date_to_string(year, month, day, format)
  end


  # Converts year, month, day to count of days since 0000-01-01.
  @doc false
  def date_to_iso_days(0, 1, 1) do
    0
  end
