Quarter of Year Calculator
Calendar quarters divide the year into four equal three-month periods, each used extensively in business reporting, financial planning, tax filing, and project management. Knowing which quarter a date falls in, when that quarter starts and ends, and how far through the quarter you are helps with deadline tracking, quarterly earnings analysis, budget planning, and scheduling deliverables. Q1 covers January through March, Q2 covers April through June, Q3 covers July through September, and Q4 covers October through December. However, fiscal quarters for businesses and government agencies often use a different start month: the US federal government's fiscal year starts on October 1, while many retailers end their fiscal year in January. This calculator works with calendar quarters, meaning Q1 always starts January 1. Enter any date to find the current quarter label, the exact start and end dates of that quarter, the total number of days in the quarter, how many days have elapsed from the quarter start to your date, and how many days remain until the quarter ends. The results update instantly as you change the date.
How quarter dates and days are calculated
The quarter is determined from the month of the entered date. The quarter start and end dates are fixed by the calendar. Days elapsed and remaining are counted inclusively from the quarter start date.
qStartMonth = (quarter - 1) * 3
qStart = new Date(year, qStartMonth, 1)
qEnd = new Date(year, qStartMonth + 3, 0) // last day of final month
daysElapsed = Math.round((d - qStart) / 86400000) + 1 // inclusive
daysTotal = Math.round((qEnd - qStart) / 86400000) + 1
daysRemaining = daysTotal - daysElapsed
Worked example
For February 15, 2026 (a regular year):
- Month index: 1 (February), so quarter = Math.ceil(2/3) = Q1
- Q1 start: January 1, 2026; Q1 end: March 31, 2026
- Total days: 90 (31 Jan + 28 Feb + 31 Mar)
- Days elapsed: 31 (Jan) + 15 (Feb to date, inclusive) = 46
- Days remaining: 90 - 46 = 44
Quarter of year calculator: frequently asked questions
What are the quarters of the year?
For a standard calendar year, Q1 runs from January 1 to March 31, Q2 runs from April 1 to June 30, Q3 runs from July 1 to September 30, and Q4 runs from October 1 to December 31. Each quarter contains three calendar months. Fiscal quarters may use different start and end dates depending on the organisation.
What is a fiscal quarter?
A fiscal quarter is a three-month period used for business financial reporting and planning. Unlike calendar quarters, fiscal quarters may not align with January through December. For example, a company with a fiscal year starting July 1 would have its Q1 run from July 1 to September 30. The US federal government's fiscal year starts October 1.
How many days are in each quarter?
Q1 has 90 days in a regular year and 91 days in a leap year (due to February 29). Q2 always has 91 days. Q3 always has 92 days. Q4 always has 92 days. This means Q3 and Q4 together have 184 days, while Q1 and Q2 together have 181 days (182 in a leap year).
When does Q4 start and end?
Q4 of the calendar year starts on October 1 and ends on December 31. It always contains 92 days: 31 days in October, 30 days in November, and 31 days in December.
What quarter is March in?
March is in Q1, which runs from January 1 through March 31. Q1 contains January (31 days), February (28 or 29 days), and March (31 days), giving a total of 90 days in a regular year and 91 days in a leap year.
Official sources
- ISO 8601 date and time format: International Organization for Standardization.
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. See our methodology.