Q1, Q2, Q3 and Q4 are common abbreviations for the quarters that make up a fiscal year for a business. Q1 represents quarter one, Q2 represents quarter two, Q3 represents quarter three and Q4 represents quarter four.
Each quarter comprises three months. In a traditional fiscal year, Q1 includes the months of January through March, Q2 includes April through June, Q3 includes July through September, and Q4 includes October through December. Each quarter, a publicly-owned company is required to communicate its quarterly earnings reports to the public. It is common for the quarter and year of the report to be included together, as in the abbreviation "Q1 2015."