Quarter Start and End Dates Calculator
Find the quarter any date falls in and its exact start and end dates — for the calendar year or a fiscal year starting in April, July or October.
How it works
months since fiscal-year start = (month − start month) mod 12 · quarter = ⌊that ÷ 3⌋ + 1 · quarter start = fiscal-year start + quarter×3 months · quarter end = next quarter start − 1 day
A quarter is a three-month block. For the calendar year the quarters are Jan–Mar, Apr–Jun, Jul–Sep and Oct–Dec, but many organisations run a fiscal year starting in April, July or October, which slides every quarter accordingly. The calculator finds the fiscal-year start on or before your date, counts three-month blocks from there, and reports the block your date sits in along with its exact first and last calendar days. The end date is one day before the following quarter begins, so it correctly lands on March 31, June 30 and so on.
Worked example
For September 15, 2026 on a calendar year, the date is in Q3 2026, which runs July 1 to September 30 (92 days). It is day 77 of the quarter with 15 days remaining.
Frequently asked questions
What are the calendar-year quarters?
Q1 is January–March, Q2 April–June, Q3 July–September and Q4 October–December. Q1 and Q2 have 90–91 days (Q1 gains a day in leap years) and Q3 and Q4 have 92.
How does a fiscal year change the quarters?
If the fiscal year starts in April, fiscal Q1 is April–June, Q2 July–September, and so on. The calculator shifts every quarter boundary to match the start month you pick.
Why is the quarter end the last day, not the first of the next?
The end date is set to one day before the next quarter starts, so it correctly returns March 31 rather than April 1 — the inclusive final day of the period.
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This calculator is for educational purposes. Double-check important results before acting on them.