Omar Khayyam, who was born at Nishapur (now in Iran), produced a work on algebra that was used as a textbook in Persia until this century. He gave a rule for solving quadratic equations, he could solve special cases of the cubic, and – in a last work – seemed to have some inkling of the binomial theorem. He also worked on the reform of the Persian calendar, which was basically the Egyptian one of 365 days, introducing a sixth epagomenic (extra) day and obtaining an accurate estimate of the tropical year.