Earnings season is the period of time during which a large number of publicly traded companies release their quarterly earning reports. In general, each earnings season begins one or two weeks after the last month of each quarter (December, March, June and September).

In other words, look for the majority of public companies to release their earnings in early to mid-January, April, July and October. It is important to note that not all companies report during earnings season because the exact date of an earnings release depends on when the given company's quarter ends. As such, it is not uncommon to find companies reporting earnings between earnings seasons.

What Sets off The Season

The unofficial kickoff to earnings season is the release of earnings by Alcoa (NYSE: AA), which is a major aluminum producer and Dow Jones Industrial Average component, as it is one of the first major companies to release earnings after the end of each quarter. It also coincides with an increasing number of earnings reports being released. There is no official end to the earnings season, but it is considered to be over when most major companies have released their quarterly earnings reports, which generally occurs about six weeks after the start of the season.

For example, for the fourth quarter, you will often see an increasing number of earnings reports released in the second week of January (Alcoa typically releases at the start of the second week). About six weeks later, or near the end of February, the number of earnings reports starts to decrease to pre-earnings season levels. There is also very little time between each earnings season. For example, the earnings season for the first quarter begins in early April, which is a little over a month after the end of the fourth quarter season.

What Earnings Season Means for Investors

This is a very active time in the market as participants (analysts, traders and investors) review the earnings reports, which may affect their positions on or in a company. You can often see a lot of movement in the shares of companies releasing reports as the market reacts to the new data. It is not unheard of to see shares jump 20% or more or to see them fall by this same amount. It is also a highly active time for the financial news media, such as CNBC and The Wall Street Journal. There is extensive media coverage of the major earnings releases from a general recap of the earnings to report on whether the companies missed, met or beat analyst expectations.

Some traders look forward to earnings season, as it can be a period where they can confirm the positions they places. Shorting a stock before earnings and watching the price drop can be beneficial, as the psychological drop will usually trigger a sell-off. Conversely, a ramping up in production or revenue could result in a swift upward trajectory or stock price. Other investors sit out the season entirely, as there are too many "human" factors at play.