# File lib/aws/s3/request.rb, line 109
      def signing_string_date
        # if a date is provided via x-amz-date then we should omit the
        # Date header from the signing string (should appear as a blank line)
        if headers.detect{|k,v| k.to_s =~ /^x-amz-date$/i }
          ''
        else
          headers['date'] ||= Time.now.rfc822
        end
      end