Calendar Effect

Dictionary Says

Definition of 'Calendar Effect'

A collection of assorted theories that assert that certain days, months or times of year are subject to above-average price changes in market indexes and can therefore represent good or bad times to invest. Some theories that fall under the calendar effect include the Monday effect, the October effect, the Halloween effect and the January effect.
Investopedia Says

Investopedia explains 'Calendar Effect'

Most of the evidence for these effects is anecdotal, although there is a slight statistical case to be made for some of them, which is more than enough to encourage some investors to place their faith in them.

Proponents of the October effect, one of the most popular theories, argue that October is when some of the greatest crashes in stock market history, including 1929's Black Tuesday and Thursday and the 1987 stock market crash, occurred. While statistical evidence doesn't support the phenomenon that stocks trade lower in October, the psychological expectations of the October effect still exist.

Related Definitions

  • Weekend Effect

    A phenomenon in financial markets in which stock returns on Mondays are often significantly lower than those of the immediately preceding Friday. Some theories that explain the effect ...
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  • October Effect

    The theory that stocks tend to decline during the month of October. The October effect is considered mainly to be a psychological expectation rather than an actual phenomenon. Most ...
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  • Monday Effect

    A theory that states that returns on the stock market on Mondays will follow the prevailing trend from the previous Friday. Therefore, if the market was up on Friday, it should continue ...
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    • January Effect

      A general increase in stock prices during the month of January. This rally is generally attributed to an increase in buying, which follows the drop in price that typically happens in ...
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    • Headline Effect

      The effect that negative news in the popular press has on a corporation or an economy. Whether it is justified or not, the investing public's reaction to various headlines can be very ...
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    • Black Tuesday

      October 29, 1929, when the DJIA fell 12% - one of the largest one-day drops in stock market history. More than 16 million shares were traded in a panic selloff.
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    • Black Monday

      October 19, 1987, when the Dow Jones Industrial Average (DJIA) lost almost 22% in a single day. That event marked the beginning of a global stock market decline, making Black Monday one ...
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    • Black Thursday

      The name given to Thursday, October 24, 1929, when the New York Stock Exchange plummeted, leading to the Great Depression of the 1930s.
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