Porhalaan

The name porhalaan came from the word hala, which is derived from Sanskrit kala, "scorpion", as the practice put observation of constellations into account.

There is often an extra 13th month in the calendar that serves this purpose, originally a Hindu leap year, but in the Batak context, it is used for a different reason.

[3] 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.

All that remains of a complicated system of adjusting lunar months to the solar Zodiac is a divination calendar which is not used for the purpose of telling times.

The first day is called Aditya ("sun"), the second Soma ("moon"), Anggara (Mars), Budha (Mercury), Brihaspati (Jupiter), Syukra (Venus), and Syanaiscara (Saturn).

The word pultak ("increasing") is added to the bright fortnight days of the porhalaan when the moon phase grows, while the word cěpik ("decreasing") is added to the dark fortnight days of the porhalaan when the moon phase decreases;[5] this is obviously influenced by the Hindu shukla pasha and krishna paksha.