code: public PactDslJsonArray timestamp(String format, Date example) {
          FastDateFormat instance = FastDateFormat.getInstance(format);
          body.put(instance.format(example));
          matchers.addRule(rootPath + appendArrayIndex(0), matchTimestamp(format));
          return this;
      }
docs: Element that must match the given timestamp format
  @param format timestamp format
  @param example example date and time to use for generated bodies