code: public String whenAsText() {
          if (whenAsText == null) {
              whenAsText = DateTimeFormatter.ISO_INSTANT.format(Instant.ofEpochMilli(when()));
          }
          return whenAsText;
      }
docs: Returns the time and date of the pushed commit in
  <a href="https://en.wikipedia.org/wiki/ISO_8601#Combined_date_and_time_representations">ISO 8601
  combined date and time representation</a>.