private static long getTimeStampMillis(ASTNode childNode) {
    String childNodeText = PlanUtils.stripQuotes(childNode.getText());
    ZoneId timeZone = SessionState.get() == null ?
        new HiveConf().getLocalTimeZone() :
        SessionState.get().getConf().getLocalTimeZone();
    TimestampTZ time = TimestampTZUtil.parse(PlanUtils.stripQuotes(childNodeText), timeZone);
    return time.toEpochMilli();
  }
Analyzer for ALTER TABLE ... EXECUTE commands.
ql/src/java/org/apache/hadoop/hive/ql/ddl/table/execute/AlterTableExecuteAnalyzer.java