The first trading day after the weekend during the 1987 market crash was called Black Monday.
Black Monday was October 19, 1987, when stock markets around the world plunged. The Dow Jones Industrial Average fell 22.6%, and major indexes in Hong Kong, Australia, the United Kingdom, and other markets also recorded dramatic declines. The event’s name refers to the Monday trading session, rather than to a specific company or financial instrument.
The timing mattered because selling pressures accumulated across international time zones. Investors reacted to concerns about valuations, interest rates, trade imbalances, and market mechanics. Program trading and portfolio insurance may have accelerated the downward movement, although economists continue to debate the relative importance of each factor.
The label can be confused with Black Tuesday in 1929 and Black Thursday in the same year. Black Monday is also used for other market crashes, so the year is important when identifying the 1987 event. The crash prompted reforms including coordinated trading halts and circuit breakers.