The Ndebele people like other Africans had three calendars to determine time and seasons : the Cosmic, Solar and Lunar calendars. These calendars are a product of African cultural astronomy.
The Lunar calendar comprised of 13 months calculated at 28-day moon cycles. Each lunar month was linked to cosmic processes which in turn shaped the environmental conditions, conduct of rituals and calculation of female menstrual cycles.
The Ndebele Lunar calendar commenced in the month of Mpandula/September. This month signalled the beginning of intwasa or spring when new vegetation began to shoot from the earth. Mpandula is derived from the word ukuphenduka referring to the change of the colour of vegetation.
The new year was determined by observing the movement of the stars in the cosmos. The emergence of the Pleiades stellar cluster in spring kick-started a new year. These stars are known as isilimela in isiNdebele. The name isilimela is derived from the word ukulima (farming).
The Ndebele people had a broad knowledge of astronomy and umthala, the Milky Way. Some of the stars in Ndebele astronomy and cosmology included inkwenkwezi, indonsakusa, izinja, isilimela, ingulube and many more whose knowledge has been lost.
To embrace intwasa, the Ndebele had to clean up the environment and remove old bird nests from trees and clear all dead animal bodies from their environment to pave the way for rain ceremonies and rituals.
A special night was announced by the King, on which the villagers gathered to prepare ritual bonfires. The wood was gathered in large pyramid shapes and then set on fire amid singing, dancing, feasting and merry-making as they celebrated the new year.
The isilimela cluster of stars is known as chinyamutanhatu in ChiShona, kelimela in SeSotho and hhala in TjiKalanga. It is also interesting to observe that Enkutatash is a public holiday in celebration of the New Year in Ethiopia and it is also in the month of September! (Source: @RealMzalaTom)