# File lib/uber-s3/operation/object/http_cache.rb, line 55
      def expires=(val)
        if val.is_a?(String)
          self.expires = val
        elsif val.is_a?(Time)
          # RFC 1123 format 
          self.expires = val.strftime("%a, %d %b %Y %H:%I:%S %Z")
        end
      end