Yoruba ritual time runs on a week of four days, the ose. It is not a subdivision of anything: the round simply repeats, and it does so continuously, which means it never lines up with a seven day week and never has to. Each of the four days belongs to an orisha or to a group of them, and that assignment is what the week is for. The day fixes when a particular shrine is served, when its devotees attend, and, historically, when the market that shared its name was held.
The usual assignments name Ifa and Orunmila, Ogun, Sango and Obatala, and other orisha are attached alongside them, so that a day of Obatala may also carry Sopona and the ancestral masquerades. The order of the four and the names given to them vary between towns, which is what one would expect of a system that was regulated locally rather than by any central authority, and any list presented as the Yoruba week is really the list of a particular place.
The market cycle is the part of the system an outsider would notice first. Neighbouring towns held their markets on different days of the round, so that a trader could work a circuit of four and be somewhere different each day. Ritual time and economic time were the same time.