code: public PactDslJsonArray timestamp(String format) {
        FastDateFormat instance = FastDateFormat.getInstance(format);
        body.put(instance.format(new Date(DATE_2000)));
        generators.addGenerator(Category.BODY, rootPath + appendArrayIndex(0), new DateTimeGenerator(format));
        matchers.addRule(rootPath + appendArrayIndex(0), matchTimestamp(format));
        return this;
      }
docs: Element that must match the given timestamp format
  @param format timestamp format