The Badí calendar is based on the solar year of 365 days, 5 hours, and 50 odd minutes. The year consists of 19 months of 19 days each (i.e. 361 days), with the addition of four extra days (five in a leap year). The Báb did not specifically define the place for the intercalary days in the new calendar. The Kitáb-i-Aqdas resolves this question by assigning the "excess" days a fixed position in the calendar immediately preceding the month of 'Alá, the period of fasting. For further details see the section on the Bahá'í calendar in The Bahá'í World, volume XVIII.