Omar Khayyam completes the Jalali calendar

1079

Commissioned by Malik Shah, a team of astronomers led by Khayyam produced a new Persian solar calendar of remarkable accuracy, more precise than the Gregorian reform would be five hundred years later. It is still the basis of the Iranian calendar in use today across modern Iran and Afghanistan. The observatory at Isfahan where Khayyam worked also produced important advances in algebra and geometric theory.