If you want the formatted string for your template in the format “month-day-year” there are a few options. You don’t need Timex but if it is already in use in your project there is no reason not to use it I guess. Here are some ways to format a Date struct:

defmodule DateFormatTest do
  use ExUnit.Case

  @date ~D[2021-07-22]
  @formatted_date "07-22-2021"

  test "format date with Calendar.strftime" do
    assert Calendar.strftime(@date, "%m-%d-%Y") == @formatted_date
  end

  test "format date with Timex.format" do
    assert Timex.format!(@date, "{0M}-{0D}-{YYYY}") == @formatted_date
  end

  test "format date with Timex.format and :strftime" do
    assert Timex.format!(@date, "%m-%d-%Y", :strftime) == @formatted_date
  end
end