private static StringBuilder ymdhms(
      StringBuilder b, int year, int month, int day, int h, int m, int s) {
    ymd(b, year, month, day);
    b.append(' ');
    hms(b, h, m, s);
    return b;
  }
Appends year-month-day and hour:minute:second to a buffer; assumes they are valid.
amoro-format-mixed/amoro-mixed-flink/amoro-mixed-flink-common/src/main/java/org/apache/amoro/flink/util/DateTimeUtils.java