classes.rb

class Foo
  @start = Time.now.to_i
  def self.start
    @start
  end

  def make_another_class
    Class.new do
      @start = Time.now.to_i
      def self.start
        @start
      end
    end
  end
end

f = Foo.new
puts "F's start was defined at #{Foo.start}"
sleep(2)
c = f.make_another_class
puts "C's start was defined at #{c.start}"

output

F's start was defined at 1352502381
C's start was defined at 1352502383