Akihito is sworn in as Emperor of Japan. His accession to the throne followed the death of his father, Emperor Hirohito, on the same day.

The Khmer Rouge government of Cambodia is overthrown. Vietnamese forces captured the Cambodian capital Phnom Penh that day.

The first transatlantic telephone service is established. A 3-minute call between New York and London cost about $45 USD, which is roughly $550 in today's dollars.

Hot air balloon crosses the English Channel. French inventor Jean-Pierre Blanchard took about 2½ hours to fly from Dover (UK) to Guînes (France).

Galileo Galilei discovers the Galilean Moons. The Italian astronomer spotted the four largest moons of Jupiter that day: Io, Europa, Ganymede, and Callisto.