The Priest's Divination Tool
The Batak people of North Sumatra did not use their traditional calendar to tell time. Instead, the porhalaan, as it is known, was a divination tool used exclusively by a ritual specialist called a datu. The datu consulted the calendar to determine auspicious and inauspicious days for events like harvests, ceremonies, or travel. This luni-solar calendar system is based on 12 months, each with 30 days. An occasional 13th month could be added, not necessarily to align with the solar year, but as an extra protective measure when calculating favorable dates.
The calendar itself was a physical object, often inscribed on a length of bamboo or a buffalo bone. It typically appeared as a grid of 12 or 13 rows (months) and 30 columns (days). The name porhalaan derives from the Sanskrit word kala, meaning scorpion. This connects to the calendar's astronomical roots; the Batak new year begins on a new moon in May when the constellation Orion sets in the west and Scorpius rises in the east. This knowledge, along with other magical formulas and recipes, was recorded by the datu in accordion-style bark books called pustaha.
A Three-Tiered Universe
Batak cosmology structures the universe into three interconnected realms: the Upper World (Banua Ginjang), the Middle World (Banua Tonga), and the Underworld (Banua Toru). The supreme deity, Debata Mulajadi Nabolon, is the creator of this tripartite system and presides over all three realms. The Upper World is the home of gods and ancestral spirits, while the Underworld is the place of entities like the cosmic serpent-dragon Naga Padoha. The Middle World is the field of humanity, suspended between the divine powers above and the chthonic forces below.
The datu was the intermediary between these worlds. The porhalaan and the accompanying knowledge in the pustaha were important guides for navigating the influences of the other worlds on human affairs. The script used to write this information is called Surat Batak, which is derived from the ancient Brahmi script of India. The datu wrote using a special instructional language called hata poda. The ink was made from organic materials like ground charcoal and resinous wood, and the text was incised into materials like bamboo or tree bark. These artifacts represent a system for understanding and ordering humanity's place within the cosmos.