A 9/80 work schedule is a US compressed arrangement: 80 hours worked over nine days instead of ten, giving every other Friday off. Eight nine-hour days, one eight-hour day, then the tenth day free.
For workplace teams, 9/80 creates a predictable attendance rhythm: alternating light Fridays that services and space planning can follow. It sits alongside the four-day week as a structured alternative to ad-hoc flexibility.