March 31’s history brings together people and systems that changed how the world was understood and connected. In 1596, René Descartes was born; his “I think, therefore I am” became a defining statement of modern philosophy, while the coordinate system bearing his name helped link algebra and geometry. In 1854, Commodore Matthew Perry signed the Convention of Kanagawa with Japan. The agreement opened selected Japanese ports to American ships and trade, beginning a major shift in the country’s relations with the outside world rather than instantly erasing its long-standing restrictions.
The day’s later milestones turn from ideas and diplomacy to public spectacle and shared time. Paris inaugurated the Eiffel Tower in 1889 as part of the World’s Fair marking the centenary of the French Revolution; a structure built for the exposition became an emblem of the city. In 1918, the United States first put daylight saving time into effect, seeking to conserve energy during World War I. As March closes and spring advances, the list has a sense of transition: each event marks a threshold, whether in thought, international contact, the city skyline, or the daily clock. Together, they suggest that change can arrive through an argument, an agreement, a landmark, or an adjustment to routine.