presto-parquet/src/main/java/io/prestosql/parquet/ParquetTimestampUtils.java/ParquetTimestampUtils/getTimestampMillis
class ParquetTimestampUtils:    public static long getTimestampMillis(Binary timestampBinary)
    {
        if (timestampBinary.length() != 12) {
            throw new PrestoException(NOT_SUPPORTED, "Parquet timestamp must be 12 bytes, actual " + timestampBinary.length());
        }
        byte[] bytes = timestampBinary.getBytes();

        // little endian encoding - need to invert byte order
        long timeOfDayNanos = Longs.fromBytes(bytes[7], bytes[6], bytes[5], bytes[4], bytes[3], bytes[2], bytes[1], bytes[0]);
        int julianDay = Ints.fromBytes(bytes[11], bytes[10], bytes[9], bytes[8]);

        return julianDayToMillis(julianDay) + (timeOfDayNanos / NANOS_PER_MILLISECOND);
    }