#OnThisDay in 1884 The International Meridian Conference referenced mean solar time to the 24 standard meridians each of 15 degrees longitude. The international date line was then established to generally follow the 180th meridian in the Pacific Ocean.
#OnThisDay in 1667, Isaac Newton became a fellow at Trinity College, Cambridge. He had earned his bachelor's degree in 1665 and then spent two years at home in Lincolnshire inventing much of differential and integral calculus while Cambridge was closed due to the plague. (@MacTutor)
#OnThisDay in 1848, Karl Weierstrass became a mathematics teacher at the Catholic Gymnasium in Braunsberg, Germany, his third such position. That year he taught mathematics for 19 hours per week, took over the geography class after Easter, and received a special note of thanks for helping out in the gym! (@MacTutor)
(High schools at that time must have been damn demanding!)