TheBorana calendar is acalendrical system used by theBorana Oromo, a people living in southernEthiopia and northernKenya. The calendar was reported to have been developed around 300 BC found atNamoratunga. However, reconsideration of the Namoratunga site led astronomer and archaeologistClive Ruggles to question the relationship between the calendar and the Namaratunga megaliths.^[1] TheBorana 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-stellarcalendar system.^[2][3]

A lunar-stellar calendar, theBorana Calendar relies on astronomical observations of themoon in conjunction with seven particular stars or constellations. Borana months (Stars/Lunar Phases) are Bittottessa (Triangulum), Camsa (Pleiades), Bufa (Aldebaran), Waxabajjii (Bellatrix), Obora Gudda (CentralOrion-Saiph), Obora Dikka (Sirius), Birra (full moon), Cikawa (gibbous moon), Sadasaa (quarter moon), Abrasa (large crescent), Ammaji (medium crescent), and Gurrandala (small crescent).^[2][3]

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.

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

The first day of the new year inBorana calendar starts in the month of "Bittootessa" and the day name "Bitta Kara". This is whenTriangulum is in conjunction with the newmoon. 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 theastronomical observation. The third month starts when one spots the new moon rising "in conjunction with" the star Aldebaran. This continues down the list of sixBorana star positions for the first six months.^[3][4]

• Namoratunga

• Borana Oromo
• Culture of Ethiopia
• Specific calendars

• Articles with short description
• Short description matches Wikidata
• Use dmy dates from February 2023