Part I. History, Religion, Politics and Time. Calendars: an introduction; The Islamic calendar; Time, the Qur'an and science -- Part II. A Medieval Case Study: Cosmology, Technology and Five Eastern Calendars Through an Islamic Lens. The making of a medieval scientist's career: Abu al-Rayhan al-Biruni; The life and works of al-Biruni; Calendars by the bushel -- Part III. How Daily Muslim Rituals are Still Performed 'on Time'. 'Time sticks': regulating the Islamic day.