The :calendrical runtime supervisor.

Owns the processes Calendrical needs at runtime and registers Calendrical with Localize as the provider of its calendars:

• Calendrical.YearCache owns the table in which the calendars reckoned by astronomy keep what they work out about a year.

• Calendrical.Compiler creates the calendars made at runtime, such as a territory's reform calendar or a calendar made with Calendrical.new/3, one at a time.

This supervisor is started when the :calendrical application starts, so most applications need do nothing. An application that prefers to start Calendrical alongside its own processes can turn that off and add this supervisor to its own supervision tree instead.

Supervising Calendrical yourself

Mark the dependency runtime: false in mix.exs, so that the :calendrical application is not started:

# mix.exs
def deps do
  [
    {:calendrical, "~> 2.1", runtime: false}
  ]
end

Then add the supervisor to the application's tree, after Localize.Supervisor when Localize is supervised the same way:

# lib/my_app/application.ex
def start(_type, _args) do
  children = [
    MyApp.Repo,
    Calendrical.Supervisor,
    MyAppWeb.Endpoint
  ]

  Supervisor.start_link(children, strategy: :one_for_one)
end

Calendrical's own dependencies are then not started either, and its calendars need two of them. Astro loads the JPL ephemeris the calendars reckoned by astronomy use: list Astro.Supervisor before this supervisor, or let this supervisor start the :astro application, which it does when Astro is not started. Localize formats, parses and localizes dates: list Localize.Supervisor before the processes that use them. The supervision guide describes both, and what a release needs.