Igbo Market Week

The izu, the Igbo week, runs only four days, Eke, Orie, Afo and Nkwo, and the four names do double duty as the days on which a locality's principal markets are traditionally held in rotation, so towns across Igboland still carry the day names built into their own place names, an Eke market town or an Afor market town identifying itself by which day of the cycle its market falls on.

Traditional reckoning builds larger units from this four day base rather than borrowing a seven day week or a thirty day month from outside: seven izu make an onwa, a twenty eight day month tracking the moon closely enough to serve as a lunar proxy, and thirteen onwa make an afo, a year of roughly three hundred sixty four days. Each of the four days is bound to its own spirits and observances rather than being interchangeable, so the calendar carries a religious charge on every one of its four positions rather than concentrating ritual significance on a single sabbath-like day the way a seven day week often does. Igbo oral tradition, recorded in detail by early twentieth century ethnographers working directly with Igbo communities, holds that the four day week and its market-spirit associations were established through the religious authority of Nri, the priest kingship whose ritual influence historically extended across much of Igboland.

The izu is not a reconstructed or ceremonial survival. It remains the working week by which markets are scheduled across Igboland today, run alongside the Gregorian week rather than replaced by it, so a given date can be described by either reckoning depending on context: civil affairs by the Gregorian calendar and market timing by the older four day cycle.

Among practitioners of Odinani, Igbo traditional religion, and in syncretic practice that blends indigenous observance with Christianity, the four days retain their distinct ritual associations, and which day of the izu a person or an event falls on can still carry meaning beyond simple scheduling. The four day week's survival alongside, rather than beneath, the imported Gregorian calendar is itself notable: unlike calendars that were formally replaced by colonial administration, the izu kept its practical function because the markets it timed continued to matter economically, giving the reckoning a durability that purely religious calendars without an economic anchor have sometimes lacked. The atlas records the tradition attributing its institution to Nri as oral history rather than as settled chronology, since the surviving documentation comes from ethnographic recording long after the tradition describes its own origin, a gap no source has yet closed.