Q1, Q2, Q3, Q4... this is just how the year is divided up into quarters for financial reporting. Usually these are January, February and March for the first quarter; April, May and June for the second; July, August and September for the third; and October, November and December for the final quarter. This is the calendar year.
But some companies will issue annual and quarterly reporting to an entirely different schedule. It depends on the company's fiscal year (its year-end date).