Number of weekdays between two dates (elixir)

foo.ex

defmodule Foo do
  def bar(first_day, second_day) do
    days_between = Date.diff(second_day, first_day) + 1
    dow1 = Date.day_of_week(second_day)
    dow2 = Date.day_of_week(second_day)

    weekend_days =
      Kernel.floor((days_between + dow2) / 7 * 2) +
        if(dow1 == 7, do: 1, else: 0) - if(dow2 == 6, do: 1, else: 0)

    days_between - weekend_days
  end
end

d1 = elem(Date.new(2020, 9, 6), 1)
d2 = elem(Date.new(2020, 9, 19), 1)

Foo.bar(d1, d2)
|> IO.inspect(label: "result")