List<Span> subtractDay(List<Span> trace) {
    long random = ThreadLocalRandom.current().nextLong();
    return trace.stream()
      .map(s -> {
          Span.Builder b = s.toBuilder().traceId(0L, random);
          if (s.timestampAsLong() != 0L) b.timestamp(s.timestampAsLong() - (DAY * 1000L));
          s.annotations().forEach(a -> b.addAnnotation(a.timestamp() - (DAY * 1000L), a.value()));
          return b.build();
        }
      ).collect(toList());
  }
rebases a trace backwards a day with different trace.
zipkin-tests/src/main/java/zipkin2/storage/ITDependencies.java