There are four quarters in a fiscal year. They are divided by 3-month periods with the first being in January, February and March, the second taking up April, May and June, the third spanning July, August and September, and the fourth lasting for the remaining months of October, November and December.
Publicly traded companies are required by law to file quarterly reports with the U.S. Securities and Exchange Commission. The mission of the commission is to protect investors, and requiring companies to file quarterly reports gives potential and current investors access to important financial data. The fiscal year in the United States may or may not match with the calendar year.