gistfile1.rbx

class Date
  def minus_with_date(other)
    if other.class == Date
      (self.minus_without_date(other)).days
    else
      minus_without_date(other)
    end
  end
  alias_method :minus_without_date, :-
  alias_method :-, :minus_with_date
end

Date.tomorrow - Date.today # => 1.day