These are two concepts that have been explained by John Mbiti in his book African Religions and Philosophy. They are two ontological stages or dimensions of history in Swahili culture.
"Zamani is not limited to what in English is called the past...Zamani overlaps with Sasa and the two are not separable. Sasha feeds or disappears into Zamani. But before events become incorporated into the Zamani, they have to become realized or actualized within the Sasa dimension. When this has taken place, the events "move" backwards from the Sasa into the Zamani."
Sasa are spirits known by someone still alive, while Zamani are spirits not known by someone currently alive. So when one speaks of learning from the past, is this learning from time itself, or the spirits from a specific dimension or ontological stage of African culture? How can one learn from that which one does not know?