Pick a calendar date and the calculator returns the calendar quarter (Q1–Q4) plus the exact start and end dates of that quarter. Calendar quarters split the Gregorian year into four three-month blocks: Q1 is January–March, Q2 is April–June, Q3 is July–September, Q4 is October–December. Useful for SaaS metrics, public-company reporting cadences, OKR cycles, and tax filings on calendar-year basis. For non-standard quarter starts (some companies offset their fiscal year), see fiscal year. For sub-quarter granularity see day of year or week of year.
Common use cases
- SaaS / OKR quarterly planning. Most product organizations work in 13-week quarterly cycles aligned with the calendar quarter. Enter the cycle's start date to confirm Q1/Q2/Q3/Q4 and read the exact range — useful when scheduling kickoff meetings and end-of-quarter reviews months in advance.
- Tax filing deadlines (calendar year). Estimated tax payments in many jurisdictions are due quarterly on calendar-year basis (Q1 ends March 31, Q2 ends June 30, etc.). The calculator gives you the unambiguous end-of-quarter date you need on the tax form. For fiscal-year filings see the fiscal year tool.
- Public-company earnings cadence. US public companies file 10-Q reports within 45 days of each quarter end. Look up the quarter end date to know the latest legal filing deadline. Calendar Q1 ends March 31 → 10-Q due by May 15.
- Cross-region marketing campaign timing. Marketing campaigns often run within a single quarter to clean attribution. Enter the campaign start date to see the natural close-by-quarter-end window. The end date is exact (no off-by-one risk).
How it works
The calculator parses your input as a UTC date and asks date-fns for the calendar quarter (1–4) plus startOfQuarter and endOfQuarter. Quarter 1 spans Jan 1 → Mar 31 of the same year. Quarter 2 spans Apr 1 → Jun 30. Q3 is Jul 1 → Sep 30. Q4 is Oct 1 → Dec 31. The returned start and end are full Date objects pinned to the day boundary in UTC. The math is calendar-year based — for organizations that shift their fiscal year, see the dedicated fiscal year tool.
Worked examples
Mid-Q2 weekday
Enter 2026-04-27.
Result: Q2; starts 2026-04-01; ends 2026-06-30.
Q2 always covers April–June. The start and end are inclusive: April 1 is the first day of Q2 and June 30 is the last.
Mid-January
Enter 2026-01-15.
Result: Q1; starts 2026-01-01; ends 2026-03-31.
Q1 always starts on January 1 of the calendar year and ends on March 31. 90 days in a non-leap year, 91 in a leap year (because of February 29).
Last day of Q4
Enter 2026-12-31.
Result: Q4; starts 2026-10-01; ends 2026-12-31.
Q4 always ends on December 31. The end-of-year date and the end-of-Q4 date are always the same.
Edge cases & gotchas
- Q1 length differs by leap-year status. Q1 is January 1 → March 31. In a leap year that's 91 days; otherwise 90. The other three quarters have stable lengths: Q2 = 91, Q3 = 92, Q4 = 92 in both leap and non-leap years.
- Quarter start dates are pinned to day 1. startOfQuarter always returns the first day of the relevant month at midnight in the local timezone of the input. The calculator interprets your input as UTC, so the returned date is always YYYY-04-01T00:00:00Z (or similar) regardless of where you are.
- Calendar quarter ≠ fiscal quarter. Many organizations use a fiscal year that doesn't align with the calendar — the US federal government runs Oct 1 → Sep 30, Apple runs Oct 1 → Sep 30, the UK tax year runs Apr 6 → Apr 5 of the next year. For non-Jan-1-aligned organizations, use the fiscal year tool which lets you pick the start month and day.
- No half-year or third-year support. The calculator only handles quarters. For half-year (H1, H2) splits, just look at whether the date is in Q1+Q2 (= H1) or Q3+Q4 (= H2). For trimester (3-month school terms in some countries), you need the school's specific calendar — there's no standard.
Frequently asked questions about Calendar Quarter Calculator
When does Q1 start and end?
Q1 starts on January 1 and ends on March 31. Same range every year (calendar Q1). Other quarters: Q2 = Apr 1 → Jun 30, Q3 = Jul 1 → Sep 30, Q4 = Oct 1 → Dec 31.
How many days are in a quarter?
Q1 has 90 (or 91 in a leap year), Q2 has 91, Q3 has 92, Q4 has 92. The slight variance comes from month lengths and the Feb 29 leap day. For a leap-year breakdown, use the day of year tool to see the cumulative day numbers at quarter boundaries.
What if my company's fiscal year doesn't start in January?
Use the fiscal year tool, which lets you specify any start month and day. The calendar-quarter tool here is for organizations on a Jan-Dec fiscal year.
Is "Q1 2026" the same as "the first quarter of 2026"?
Yes. "Q1 2026" is shorthand for January–March 2026. Some companies write it "1Q26" or "Q1FY26" — the meaning is the same provided the fiscal year matches the calendar year.
How do I find which quarter a date is in without a calculator?
Take the month number (1–12), divide by 3, round up: Math.ceil(month / 3). January is month 1 → Q1. April is month 4 → Q2. October is month 10 → Q4. The calculator does this for you and adds the explicit start/end dates so you don't have to look those up separately.
Are the start and end inclusive?
Yes — both ends are inclusive calendar dates. Q1 starts on January 1 (the first day of the quarter) and ends on March 31 (the last day, the entire 24 hours). When working with timestamp ranges in code, treat the end date as "less than April 1" to avoid the boundary-second confusion.
Glossary
- Calendar quarter
- A three-month block of the calendar year. Q1 = Jan–Mar, Q2 = Apr–Jun, Q3 = Jul–Sep, Q4 = Oct–Dec. Always anchored to the Gregorian calendar.
- Fiscal quarter
- A quarter aligned to a company's fiscal year, which may not match the calendar. Apple's Q1 runs Oct–Dec. Use the fiscal year tool for non-Jan fiscal years.
- 10-Q report
- Quarterly financial filing required of US public companies, due within 40–45 days of quarter end. Aligned to fiscal quarter, not necessarily calendar quarter.
- OKR cycle
- Quarterly objectives-and-key-results planning cycle popularized by Google. Usually 13 weeks (one calendar quarter), aligned to calendar Q1–Q4 in most organizations.