Mathematical scholarship continues beyond Baghdad

Alongside religious and linguistic studies, scholars taught inheritance arithmetic, astronomy, timekeeping and related mathematical subjects.

Al-Azhar shows how mathematics was transmitted through teaching communities rather than only through famous books and individuals.

Students from Africa, Asia and the wider Islamic world carried methods and texts across linguistic and political boundaries.

The Abbasid caliph surrendered on 10 February 1258, followed by the sack of a city central to centuries of scientific exchange.

Libraries and institutions suffered catastrophic loss, although the familiar story that all books were thrown into the Tigris cannot be treated as a precise inventory.

The destruction of Abbasid institutions redirected scholars and resources, reshaping rather than ending mathematics in the Islamic world.

Pope Gregory XIII issued the bull Inter gravissimas. It reformed leap-year rules to bring the civil calendar closer to the solar year.

The reform used astronomical calculation and a revised leap-year cycle to limit the drift of the equinox through the calendar.

The calendar illustrates how numerical models become social institutions through political and religious authority.

Catholic states adopted the reform first, while other societies accepted, adapted or resisted it at different times; calendar history was not a single global switch.