# File lib/rbot/core/utils/httputil.rb, line 252
    def revalidate(resp = self.response)
      @count = 0
      self.use
      self.date = resp.key?('date') ? Time.httpdate(resp['date']) : Time.now

      cc = resp['cache-control']
      if cc && (cc =~ /max-age=(\d+)/)
        self.expires = self.date + $1.to_i
      elsif resp.key?('expires')
        self.expires = Time.httpdate(resp['expires'])
      elsif lm = resp['last-modified']
        delta = self.date - Time.httpdate(lm)
        delta = 10 if delta <= 0
        delta /= 5
        self.expires = self.date + delta
      else
        self.expires = self.date + 300
      end
      # self.expires = Time.now + 10 # DEBUG
      debug "expires on #{self.expires}"

      return true
    end