Calculate how many business days are for an option in the market taking in mind T+2 formula

DateUtils.ex

defmodule Module.DateUtils do
  @doc """
  Functions to help with dates.
  """

  @holidays [
    # New year
    ~D[2023-01-01],
    # Christmas
    ~D[2023-12-25]
  ]

  @spec business_days_from_today(integer) :: {Date.t(), Integer.t()}
  def business_days_from_today(count) when is_integer(count) do
    today_in_local_timezone()
    |> calculate_business_days(count, 0)
  end

  def today_in_local_timezone do
    timezone_offset_hours = -3

    DateTime.utc_now()
    |> DateTime.add(timezone_offset_hours * 3600)
    |> DateTime.to_date()
  end

  defp calculate_business_days(date, 0, acc), do: {date, acc}

  defp calculate_business_days(date, count, acc) do
    next_day = Date.add(date, 1)

    is_business_day?(next_day)
    |> maybe_add_day(next_day, count, acc)
  end

  defp is_business_day?(date) do
    date
    |> Date.day_of_week()
    |> is_weekday?() and
      date not in @holidays
  end

  defp is_weekday?(day_of_week) when day_of_week in 1..5, do: true
  defp is_weekday?(_), do: false

  defp maybe_add_day(true, next_day, count, acc),
    do: calculate_business_days(next_day, count - 1, acc + 1)

  defp maybe_add_day(false, next_day, count, acc),
    do: calculate_business_days(next_day, count, acc + 1)
end