# File lib/rubygame/clock.rb, line 280
    def calibrate( max_time = 0.5 )
      samples = []

      end_time = Time.now + max_time

      while( Time.now < end_time )
        t = Time.now
        sleep 0.01
        samples << (Time.now - t - 0.01)
      end

      average = samples.inject{|sum,n| sum + n} / samples.length

      # convert to ms, add some padding
      gran = (average * 1000).to_i + 1

      @granularity = gran

      return nil
    end