Onitsha ceremonial life involves a series of festivals, with each festival forming part of a continuum that helps to symbolically relate each aspect of social life to the wider reality. Six main festivals are celebrated in one Onitsha year. The basic sacred divisions of the year are set by the phases of the moon. The Obi proclaims each of the 28-day lunar months ONWA and defines the ceremonial sequences in terms of the seven four-day weeks OGE ISA that comprise each month.