21 October 2013 (2 years ago): Record smog closes schools, roadways, and the airport in Harbin, China.

21 October 2005 (10 years ago): Images of the dwarf planet Eris are taken and subsequently used in documenting its discovery by the team of Michael E. Brown, Chad Trujillo, and David L. Rabinowitz.

21 October 1994 (21 years ago): In Seoul, 32 people are killed when the Seongsu Bridge collapses.

21 October 1987 (28 years ago): Jaffna hospital massacre is carried out by Indian Peace Keeping Force in Sri Lanka killing 70 ethnic Tamil patients, doctors and nurses.

21 October 1986 (29 years ago): In Lebanon, pro-Iran kidnappers claim to have abducted American writer Edward Tracy (he is released in August 1991).

21 October 1983 (32 years ago): The metre is defined at the seventeenth General Conference on Weights and Measures as the distance light travels in a vacuum in 1/299,792,458 of a second.

21 October 1977 (38 years ago): The European Patent Institute is founded.

21 October 1328 (687 years ago): Hongwu Emperor of China (d. 1398) was born

21 October 1650 (365 years ago): Jean Bart, French admiral (d. 1702) was born

21 October 1887 (128 years ago): Mihkel Müller, Estonian wrestler (d. 1970) was born

21 October 1600 (415 years ago): Shima Sakon, Japanese samurai (b. 1540) died

21 October 1775 (240 years ago): Peyton Randolph, American lawyer and politician, 1st President of the Continental Congress died