Adding extensions to a stdlib class in a ruby on rails project

where would I place additions to stdlib classes in a rails project? Let's say somethi开发者_开发问答ng like:

class Date
  def foo
    'foo'
  end
end

I thought about the initializer folder but it somehow felt wrong. Ideas?

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Quite on the contrary, config/initializers is the right place to put this code. I usually create a folder there and put these extensions into separate files named by the name of the corresponding class (date.rb in your case).