code: @CheckForNull
    public Date getDateTime(String key) {
      String value = getString(key);
      if (StringUtils.isNotEmpty(value)) {
        return DateUtils.parseDateTime(value);
      }
      return null;
    }
docs: Effective value as {@link Date}, with time fields. Format is {@link DateUtils#DATETIME_FORMAT}.
  
  @return the value as a {@link Date}. If the property does not have value nor default value, then {@code null} is returned.
  @throws RuntimeException if value is not empty and is not in accordance with {@link DateUtils#DATETIME_FORMAT}.