presto-spi/src/main/java/io/prestosql/spi/type/DateTimeEncoding.java/DateTimeEncoding/updateMillisUtc
class DateTimeEncoding:    public static long updateMillisUtc(long newMillsUtc, long dateTimeWithTimeZone)
    {
        return pack(newMillsUtc, (short) (dateTimeWithTimeZone & TIME_ZONE_MASK));
    }