On this day in 1983, the discovery of the HIV virus that causes AIDS was published in the journal Science by Luc Montagnier.
On this day in 1989, the Chinese authorities declared martial law in the face of pro-democracy demonstrations, setting the scene for the Tiananmen Square massacre.
On this day in 1996, The Supreme Court of the United States ruled in Romer v. Evans against a law that would have prevented any city, town or county in the state of Colorado from taking any legislative, executive, or judicial action to protect the rights of gays and lesbians.
On this day in 2010, a social media event was celebrated in response to the Muslim extremists' reaction to images of Mohammed.