Timkat, the Ethiopian feast of the Epiphany, begins with this letter. It commemorates the baptism of Christ, and it is kept in January over three days with the largest processions of the Ethiopian year.
What happens is that the tabot of each church, the consecrated tablet from its sanctuary, is carried out wrapped in cloth on the head of a priest and taken in procession to a body of water, a river, a pool or a reservoir prepared for the purpose. The night is spent there in vigil and chant. In the morning the water is blessed and the people are sprinkled or immerse themselves, and the tabot is carried back. For most of the congregation this is the one occasion in the year when the tabot leaves the sanctuary and travels.
The feast is worth describing carefully because it makes the logic of the tabot visible. A church is a church because of the tablet in it, so a procession is not a display of an object belonging to the building; it is the building's centre moving through the town with everyone behind it. Reading the tabot as an Ethiopian equivalent of a Western altar stone misses that. The atlas describes the practice and leaves the comparison alone.
The feast falls in the Ethiopian month of Terr, which lands in January, and it takes its date from the Ethiopian calendar rather than from a Western one, so a visitor working from a Gregorian diary can find it a day out from what a guidebook says. That is a small instance of a general point about this tradition. Its year is calculated by its own rules and converted afterwards, if at all.