code: public static @Nullable Date get(@Nullable Page page) {
      if (page == null) {
        return null;
      }
      Calendar lastModified = page.getLastModified();
      if (lastModified != null) {
        return lastModified.getTime();
      }
      else {
        return null;
      }
    }
docs: Get modification date of page
  @param page CQ page
  @return Modification date or null if none set