"The antiquity and the originality of the Somali calendar is further supported by the belief that the ancient Eastern Cushitics, to which the Somalis belong, developed a sophisticated calendar based on detailed astronomical knowledge by the first millennium BCE (Before Common Era). Researchers have studied the archeo-astronomical nature of two megalithic sites on the southwest part of Lake Turkana, northwest of present Kenya."
It was also used by mostly farmers and herders to determinate the weather and seasons.
We all know why Osmanya never became official and that was because Siad barre repressed it and pushed for Latin which is a failure.