Igbo Calendar contains 4 days in a week, 7 weeks in a month(onwa), 28 days in a month, 13 months in a year, 91 weeks in a year(izus), and 364 days in a year.
Igbo are allowed to work for three days in the week. One day is set aside for rest, usually Eke, but any day can be chosen by the town.
Igbo Calendar.org, retrieved 21-March-2012
Igbo Userguide.org, retrieved 21-March-2012