🗂When does the quarter start and end?

Try one of these too

“Q3” is not a date. It is a label whose meaning depends on which year the person using it is counting from, and in a single meeting it can plausibly mean July to September, April to June, or October to December. The fastest way to settle it is to say the months out loud, which is why this tool always prints the range next to the label.

Three year bases, the same twelve months

The same stretch of calendar, cut three ways. Day counts are computed from the dates themselves.

Read across the first row and the problem is obvious: three organisations can all be “in Q1” on completely different days, and two of them are in a quarter that the third calls something else.

The quarters are not the same length

Calendar quarters run 90, 91, 92 and 92 days in a common year, and 91, 91, 92, 92 in a leap year. As shares of the year that is 24.7 per cent for Q1 against 25.2 per cent for Q4 — a two-day spread that never appears in a quarter-on-quarter comparison but is always in the numbers.

Two days is about 2.2 per cent of a quarter. For anything measured per day — revenue, output, headcount hours, energy use — that is the size of a difference people routinely attribute to performance. The fix is either to divide by the days in the quarter or to move to a calendar where the quarters are equal, which is exactly what the retail 4-5-4 calendar does with thirteen-week quarters of 91 days each.

Q1 of what? The naming traps

The federal year is named for its end. FY2027 begins in October 2026. A grant, a budget line or a contract quoting “FY27 Q1” means the autumn of 2026, three months before the calendar year of that name starts at all.

The UK writes a pair, and the pair is not a range of years’ worth of work. “2026/27” is a single twelve-month period beginning 6 April 2026.

Corporation tax and income tax do not share a year in the UK. The financial year for corporation tax runs 1 April to 31 March; the tax year for individuals runs 6 April to 5 April. Five days apart, and they are genuinely different periods.

A company’s Q1 is whatever the company says it is. The FAQ below has the well-known examples; the general rule is that you cannot infer it and have to look it up.

Working out which one you are on

Four questions settle it in most cases.

1. Who is asking? A government department, a tax return, a listed company and a marketing plan will each have a different default.
2. What is the year called? A single year with no slash suggests a US federal or company FY named for its end; a pair with a slash suggests a tax year that straddles two calendar years.
3. When does the reporting year end? Every other boundary follows from that one date.
4. Does the quarter end on a month end? If it does not, the quarters are probably built from 13 weeks rather than three months, and the dates will move slightly every year.

Once you know the answer, put the date into the tool above with that basis selected and every boundary for the year comes out at once.

For the share of the period that has elapsed rather than the dates that bound it, use year progress. For how many of a quarter’s days are actually workable, working days in a year counts by month, and business days calculator counts between any two dates. The rest of the set is on the calendar tools page.