Borana calendar

From Infogalactic: the planetary knowledge core
(Redirected from Oromo calendar)
Jump to: navigation, search

The Borana calendar is a calendrical system developed by the Borana Oromo around 300 BC. The Borana calendar consist of 29.5 days and 12 months for a total 354 days in a year.The calendar has no weeks but name for each day of the month. It is a lunar-stellar calendar system.[1][2]


Main article: Namoratunga

It is believed that the Borana have developed their own calendar around 300 BC. In Namoratunga archaeoastronomical site in northern Kenya, stone pillars pointing to positions of stars used in Borana calendar were found. Namoratunga II contains 19 basalt pillars, aligned with 7 star systems of the Borana calendar: Triangulum, Pleiades, Bellatrix, Aldebaran, Central Orion, Saiph, and Sirius. It is believed that the Borana used these astronomical observation site to develop the calendar.


A lunar-stellar calendar, the Borana Calendar relies on astronomical observations of the moon in conjunction with seven particular stars or constellations. Borana months (Stars/Lunar Phases) are Bittottessa (Triangulum), Camsa (Pleiades), Bufa (Aldebaran), Waxabajjii (Bellatrix), Obora Gudda (Central Orion-Saiph), Obora Dikka (Sirius), Birra (full moon), Cikawa (gibbous moon), Sadasaa (quarter moon), Abrasa (large crescent), Ammaji (medium crescent), and Gurrandala (small crescent).[1][2]

There are 27 names of days of a month. Hence, first two or three days are used twice at the beginning and end of a month.

Names of days of a month
1. Bita Kara 10. Gidada 19. Adula Ballo
2. Bita Lama 11. Walla 20. Maganatti Jarra
3. Gardaduma 12. Ruda 21. Maganatti Britti
4. Sonsa 13. Basa Dura 22. Garba Dura
5. Sorsa 14. Basa Ballo 23. Garba Balla
6. Rurruma 15. Areri Dura 24. Salban Dura
7. Algajima 16. Areri Ballo 25. Salban Balla
8. Lumasa 17. Carra 26. Salban Dullacha
9. Arb 18. Adula Dura 27. Garda Dullacha

Months can be identified by moon phase in relation to seven stars or star groups. They star groups are Triangulum (called Lami by Borana), Pleiades (called Busan by Borana), Aldebaran (called Bakkalcha by Borana), Bellatrix (called Algajima by Borana), central Orion (called Arb Gaddu by Borana), Saiph (called Urji Walla by Borana), and Sirius (called Basa by Borana) star systems.

Months and Star System

Month name Star group Borana name

for star group

1. Bittottessa Triangulum Lami
2. Camsa Pleiades Busan
3. Bufa Aldebaran Bakkalcha
4. Wacabajjii Belletrix Algajima
5. Obora Gudda Central Orion-Saiph Arb Gaddu
6. Obora Dikka Sirius Basa
7. Birra full moon
8. Cikawa gibbous moon
9. Sadasaa quarter moon
10. Abrasa large crescent
11. Ammaji medium crescent
12. Gurrandala small crescent

The first day of the new year in Borana calendar starts in the month of "Bittootessa" and the day name "Bitta Kara". This is when Triangulum is in conjunction with the new moon. After that, the calendar simply counts the day names through the month based on that first astronomical observation - conjunction of the new moon at the beta Triangulum position. The next month begins when the new moon is in conjunction with the next star or star system, in this case, Pleiades (a blue star cluster). This occurs 29.5 days after the start of the first month. However, the calendar runs out of day names a couple of days early. This is acceptable since the names of the days that started the month are also the names of the days that finish the month. This is the same for all the months, adjusted for the observations, of course, allowing a variation of a day or two here and there based on the astronomical observation. The third month starts when one spots the new moon rising "in conjunction with" the star Aldebaran. This continues down the list of six Borana star positions for the first six months.[2][3]

See also



  1. 1.0 1.1 Doyle, Laurance R. The Borana Calendar REINTERPRETED. Current Anthropology. Physics and Astronomy Department, University of California, Santa Cruz, at NASA Ames Research Center, Space Sciences Division, M.S., retrieved: 7 April 2010.
  2. 2.0 2.1 2.2 Asmarom Legesse. Gada Three Approaches to the Study of African Society. The Free Press A Division of McMillan Co. Inc, 1973
  3. Laurance R. Doyle. Ancient African Skies. The SETI Institute, 7 April 2005; retrieved: 28 September 2014