According to tradition, the indigenous peasant Juan Diego encountered an apparition of the Virgin Mary at Tepeyac Hill, who left her image imprinted on his cloak. The event became a cornerstone of Mexican and Latin American Catholicism, fusing indigenous and Spanish religious identity. December 12 remains one of the most widely celebrated feast days in the Americas.

Meeting in Philadelphia, Pennsylvania's ratifying convention approved the new U.S. Constitution by a vote of 46 to 23, making it the second state to join the union under the new charter, just five days after Delaware. The vote followed heated exchanges with Anti-Federalists who feared a strong central government, foreshadowing debates that would shape the Bill of Rights.

Guglielmo Marconi and his assistant George Kemp used a kite-borne antenna atop Signal Hill in Newfoundland to receive three faint clicks, the Morse code letter 'S', transmitted from a station in Poldhu, Cornwall, over 2,200 miles away. Many scientists had insisted radio waves could not follow the Earth's curvature; Marconi's feat proved wireless communication could span oceans and launched the age of global radio.

Following Finland's declaration of independence on December 6, 1917, France extended formal diplomatic recognition on December 12, one of the earliest nations to do so. The recognition came as the Russian Empire collapsed into civil war, giving Finland a rare window to break away and establish itself as a sovereign state after over a century under Russian rule.

Soyuz TM-7, launched days earlier, docked with the Mir space station carrying Soviet cosmonauts Alexander Volkov and Sergei Krikalev alongside French astronaut Jean-Loup Chrétien, who conducted a spacewalk and joint research during his stay. The mission underscored a surprising thread of Franco-Soviet space collaboration even as the wider Cold War ground on.

American Special Forces, CIA paramilitary teams, and Afghan militia fighters pressed a large-scale assault on cave and tunnel complexes in the White Mountains of Tora Bora, believed to be sheltering Osama bin Laden and hundreds of al-Qaeda fighters. Heavy bombing and ground fighting continued for days, but bin Laden ultimately slipped across the border into Pakistan, a failure that would shape the next decade of the war on terror.