Ibos have a four day calendar, where four days make a week and 7 weeks make a month. These fours days; Eke, Orie, Afo, Nkwo are also known as the four market days. Occasionally the Ibos try to discern which of the market days corresponds to a given Gregorian calendar date, especially to know when to schedule events such as marriages, naming ceremonies etc. There were few people who had the means and resources to find the Igbo market day for a given date, whether a future or past date.
But now that means/resource is now online free and accessible to all. Your can find the Igbo market day of any given Gregorian calendar date at find Igbo market day online.