Indigenous Knowledge about Time-Keeping: Astronomical Aspects of The Batak Calendar

The Batak calendar year is often referred to in literature as a lunar year. However, the Batak calendar system reveals that it is set up to compensate for the difference between the lunar year and the solar year. This is of great practical importance insofar as a solar year is primarily useful for planning agricultural work. Nevertheless, they were able to maintain peace and stability within their territorial organizations, called bius, and they were able to organize the co-operation necessary to pursue irrigated rice cultivation. This study is a field research report on an investigation into the subject of the indigenous knowledge of time-keeping, as it was of practical importance to the communal organization of agricultural activities in traditional Toba Batak society. The Batak's time calculation expert calculates, to put it simply, twelve months of thirty days each and calls the remainder of the solar year lobi-lobi ni bulan (the remainder of the month) or lamadu, which makes the lunar and solar years congruent again. As far as is known, the years themselves were not counted in Batak culture, or, if so, only to a limited extent, but the days of the year were counted. Usually there was always at least one specialist in time calculation within a bius organization, because the reliable determination of time was essential to the ritual as well as to the agricultural course of the year.