The Borana calendar

A calendar read from the sky

The Borana are a branch of the Oromo people living in southern Ethiopia and northern Kenya, mostly as cattle herders. Their calendar is kept by specialist elders who watch the night sky. It is lunar-stellar: each month begins when the new moon is first seen, so it lasts 29 or 30 days, and twelve months make a year of about 354 days. Which month it is depends on where the moon stands against a set of seven stars or star groups. The anthropologist Marco Bassi records month names that refer to stars, such as Camsa for the Pleiades and Obora Dikka for Sirius, alongside names taken from the phases of the moon.

There are no weeks. A separate cycle of 27 named days runs alongside the months. Because 27 days is shorter than a lunar month, the two cycles drift against each other, and the combination of a day name and a month name identifies a particular day.

Why it matters to the Borana

The calendar is not only a way of counting days. It sets the time of ceremonies in the Gadaa system, the Oromo form of self-government in which age-based classes take turns holding power, with leadership changing hands every eight years. UNESCO inscribed the Gada system on its Representative List of the Intangible Cultural Heritage of Humanity in 2016.

How scholars have described it

The Eritrean anthropologist Asmarom Legesse gave the first full account in his book Gada (1973). In 1986 the astronomer Laurance Doyle found astronomical inconsistencies in that account and proposed that the system works by the height of stars above the equator (their declination). Marco Bassi, who worked in the field with the Borana calendar expert Bante Abbagala, replied in 1988 that the Borana do not use declination at all. They judge the moon's position along the band of stars it travels through. He also argued that the Borana, without naming it, add an extra month from time to time so that month names stay in step with the seasons. The archaeoastronomer Clive Ruggles later reviewed the competing accounts.

These are disagreements about how the calendar works, not about whether it works. The calendar is a functioning system in daily use, and this entry is labeled Documented.

The Namoratunga question

In 1978 archaeologists proposed that a ring of stone pillars in northern Kenya, Namoratunga, was built to observe the stars of the Borana calendar about 2,300 years ago. That link is Debated, and Ruggles questioned it. The age of the Borana calendar itself is not known.