# File lib/new_relic/agent/instrumentation/queue_time.rb, line 32
        def parse_frontend_timestamp(headers, now=Time.now)
          earliest = nil

          CANDIDATE_HEADERS.each do |header|
            if headers[header]
              parsed = parse_timestamp(timestamp_string_from_header_value(headers[header]))
              if parsed && (!earliest || parsed < earliest)
                earliest = parsed
              end
            end
          end

          if earliest && earliest > now
            NewRelic::Agent.logger.debug("Negative queue time detected, treating as zero: start=#{earliest.to_f} > now=#{now.to_f}")
            earliest = now
          end

          earliest
        end