code: public static String parseFullFormat(String dateStr, String pattern, int addDays) {
          try {
              Date date = parseDate(dateStr, pattern);
              if (addDays != 0) {
                  date = addDays(date, addDays);
              }
              return DateUtils.format(date, "yyyy-MM-dd HH:mm:ss");
          } catch (Exception e) {
              return null;
          }
      }
docs: #func 获取时间的完整格式<br>
  #desc addDays为计算相对时间，可为负数
  
  @author dulin
  @version 4.0.14