Earnings Season is a quarterly event, a right of passage so to speak, that comes along every three months like clockwork.
Earnings season is the four times a year, celebrated several-week stretch from early January to early February, from early April to early May, from early July to early August, and from early October to early November in which the vast majority of the nation's corporations report their quarter's sales and earnings--hence the name earnings season.
This four-times-a-year event reflects the fact that U.S. corporations file such reports with the SEC on a quarterly basis. Since such reports are typically issued from two to five weeks after a quarter ends, and since the majority of U.S. corporations are on a calendar fiscal basis for reporting purposes, these are the four times during the year that companies report. The notable exception are the nation's retailers, which typically have their quarters end in late April, July, October, and January.
Earnings season typically gets under way with several well-known companies, e.g., Alcoa (AA), the aluminum giant, General Electric (GE), the industrial behemoth, and Intel (INTC), the semiconductor manufacturer leading the way. It is most helpful and often telling that these three major corporate names are three of the earliest reporting companies, as they represent a trio of key sectors, respectively, basic industries (Alcoa), industrial and financial services (General Electric), and technology (Intel). Each is also a member of the Dow Jones Industrial Average.
These three companies are so-called bellwethers of their respective industries or economic sectors, and they often serve as proxies for additional key reporting companies. Their effect on the stock market, particularly in the case of Intel, is considerable. If any of these companies surprises on the upside, with either revenues or earnings, or issues a negative surprise, the individual stocks can jump or fall appreciably--and take the stock market with them. That is because these reports are seen as leading indicators of other earnings reports to come in the following days. Other key early reporting names in the tech sector are Microsoft (MSFT) and International Business Machines (IBM), both of which are also Dow-30 companies.
As a rule, most American corporations report their quarterly results either before the stock market opens--often at 7:00 AM (Eastern Time), or after the market closes (4:00PM along the East Coast). This is, theoretically at least, to give as many investors as possible the time to react to these reports and to act accordingly, before trading commences.