The festival begins in Timket Eve, January 18th. (today)
According to an Ethiopian epic called Kebra Negast the Ark of the Covenant was abducted from Jerusalem and brought to Ethiopia during the first millennium BC. It is the most sacred element of the Ethiopian Orthodox Church.
Early on Timket Eve, about 2PM, replicas of the Ark, covered by silks are solemnly carried by priests from each church to a nearby body of water. They are accompanied by a procession of tens of thousands of church members and believers.




The procession is a loud and festive affair. Believers are chanting, dancing, drum-beating, horn blowing, prayer-stick-waving, and sistra (a musical instrument) rattling. It reenacts scenes described in the Old Testament.
As evening falls, priests and believers participate in an overnight vigil.
As dawn approaches a hymn is spontaneously started that spreads through the crowd.

The priest blesses the water at day break, and the celebration reaches its climax.

The festival continues until the third day which is dedicated to the Archangel Mikael. (I did not find much information about that.) On the third day the Arks are carried back to their respective churches with the same dancing, singing, and instrument playing as before.