 If the additional 13th month is not available, then the first month is simply used again for protection.Whether the 13th month is used to compensate for the difference to the solar year is not proven in the context of Batak society.The Porhalaan is usually written as a table of square boxes of 30 columns (days) of 12 or 13 rows (months) as recorded in the pustaha, the Batak magic book.