linguistic:paraphrasing
Mourning

In the West, black is commonly associated with mourning and bereavement, and usually worn at funerals and memorial services. In some traditional societies, for example in Greece and Italy, some widows wear black for the rest of their lives. In contrast, across much of Africa and parts of Asia like Vietnam, white is a color of mourning.

In Victorian England, the colors and fabrics of mourning were specified in an unofficial dress code: "non-reflective black paramatta and crape for the first year of deepest mourning, followed by nine months of dullish black silk, heavily trimmed with crape, and then three months when crape was discarded. Paramatta was a fabric of combined silk and wool or cotton; crape was a harsh black silk fabric with a crimped appearance produced by heat. Widows were allowed to change into the colors of half-mourning, such as gray and lavender, black and white, for the final six months."

A "black day" (or week or month) usually refers to tragic date. The Romans marked fasti days with white stones and nefasti days with black. The term is often used to remember massacres. Black months include the Black September in Jordan, when large numbers of Palestinians were killed, and Black July in Sri Lanka, the killing of members of the Tamil population by the Sinhalese government.

In the financial world, the term often refers to a dramatic drop in the stock market. For example, the Wall Street Crash of 1929, the stock market crash on 29 October 1929, which marked the start of the Great Depression, is nicknamed Black Tuesday, and was preceded by Black Thursday, a downturn on 24 October the previous week.