Week number within quarter
Enter a date to see which week of its calendar quarter it falls in: 20 May 2026 is in week 8 of Q2, counted from 1 April. Week 1 is always the first seven days of the quarter, so numbering resets each quarter. Free in your browser.
- Free
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- Your data stays on your device
Run — free
Worked example
- Date
- 2026-05-20
- Year
- 2,026
- Quarter
- 2
- Quarter start
- 2026-04-01
- Week number
- 8
Turn one explicit ISO calendar date into a clear, repeatable week position inside Q1, Q2, Q3, or Q4. The calculation anchors week 1 to the first day of the calendar quarter, then groups each successive seven-day period into the next week number. It never reads the current time, applies a local timezone, or consults an external calendar. That makes the result suitable for dashboards, reporting pipelines, validation rules, and tests that must produce the same answer everywhere. Send a real date in YYYY-MM-DD format and receive its normalized date, year, quarter, quarter start, and one-based week number.
How a week number within a quarter is defined
This calculator uses calendar quarters and quarter-relative seven-day blocks. Q1 begins January 1, Q2 begins April 1, Q3 begins July 1, and Q4 begins October 1. The first seven calendar dates in any quarter belong to week 1, dates eight through fourteen belong to week 2, and the pattern continues until the quarter ends.
In formula terms, the service counts completed days since the quarter start, divides that count by seven using integer division, and adds one. This is intentionally different from an ISO week-of-year number, whose weeks begin on Monday and may cross year or quarter boundaries. A quarter-relative number is more useful when a report, campaign, target, or operational cycle resets exactly at the first day of each calendar quarter.
Because quarter lengths vary, the final numbered week can contain fewer than seven days, and some quarters reach week 14. Every calculation uses the proleptic Gregorian leap-year rules, including century exceptions, so February dates behave consistently across the supported years.
Supplying and validating the date
Send one date field as an explicit ISO calendar date in the exact YYYY-MM-DD form, such as 2026-05-20. Leading or trailing prose, locale-specific ordering, timestamps, and omitted zero padding are rejected instead of guessed. Strict input is valuable in automated systems because a string like 03/04/2026 can mean different days in different countries, while the ISO form has one interpretation.
The year must fall from 0001 through 9999, the month must be 01 through 12, and the day must exist in that month. The capability does not use JavaScript Date parsing, the machine timezone, or the system clock. It extracts and validates the numeric calendar components itself, then performs bounded integer arithmetic.
As a result, replaying a stored request later gives the identical response.
Using the result in reports and automation
Quarter-relative week numbers are compact labels for work that follows a calendar-quarter cadence. A product team can compare adoption in week 3 of several quarters even when ordinary week-of-year values differ. Remember that this capability measures calendar-day blocks, not business weeks.
It does not skip weekends or holidays, start weeks on Monday, implement a 4-4-5 retail calendar, or support a custom fiscal-year beginning. Those are different conventions and should not be mixed into the same field. If users need ISO week-of-year reporting, retain a separately named value so its meaning stays clear.
For quarter progress, use this result with a date supplied by your application rather than asking a server for “today”; explicit input preserves deterministic backfills and makes historical corrections safe.
What you can do with it
Quarter performance dashboards
Label dated KPI snapshots with a consistent quarter-relative week for comparisons across successive calendar quarters.
Campaign pacing
Map an explicit activity date to the campaign quarter's current seven-day block without timezone-dependent results.
FAQ
Does week 1 start on Monday?
No. Week 1 starts on the first calendar day of the quarter, and each following block contains seven calendar days.
Is this the same as ISO week of year?
No. ISO week-of-year follows Monday-based weeks that can cross quarters. This number resets at every calendar quarter start.
Can the result reach week 14?
Yes. A calendar quarter lasts 90, 91, or 92 days, so its final one to four dates fall in quarter-relative week 13 or 14 depending on the length and placement.
Are timestamps or local date formats accepted?
No. Provide exactly YYYY-MM-DD. Strict parsing prevents timezone shifts and ambiguous day-month ordering.
When does each quarter start?
Q1 starts on 1 January, Q2 on 1 April, Q3 on 1 July and Q4 on 1 October. On each of those days the count resets, so that date is always week 1 of its quarter.
Related tools
For developers — API access
Everything on this page is available programmatically. This section is for teams who want to wire it into their own systems; everyone else can just use the tool above.
API endpoint
Prefer to automate it? One authenticated POST creates the task; the result comes back by webhook or a signed link. The same capability also runs here on the web, by email and from Telegram — and soon from our app too.
Call it from your stack
curl -X POST https://api.kit.forhosting.com/date/week-number-in-quarter \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"date":"2026-05-20"}'const res = await fetch("https://api.kit.forhosting.com/date/week-number-in-quarter", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"date": "2026-05-20"
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/date/week-number-in-quarter",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"date": "2026-05-20"
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/date/week-number-in-quarter", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"date":"2026-05-20"}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"date":"2026-05-20"}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/date/week-number-in-quarter", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"date": "2026-05-20"
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "date.week_number_in_quarter",
"status": "queued",
"_links": {
"result": "/tasks/tsk_…/result"
}
}The API is asynchronous: the call returns a task_id immediately and the result arrives by webhook. Polling is capped at 1 req/s per task.
Pricing
Published price — no tokens, no invented credits. A failed task is never charged.
Errors
| HTTP | Code | Meaning |
|---|---|---|
401 | unauthorized | Missing or invalid API key. |
402 | insufficient_balance | Your balance doesn't cover the task price. |
404 | unknown_type | That task type doesn't exist. |
429 | rate_limited | Too many requests. Use the webhook instead of polling. |
Technical notes
How a week number within a quarter is defined
The response includes quarter_start so consumers can verify the anchor rather than relying on an unstated convention.
Supplying and validating the date
February 29 is accepted only in a Gregorian leap year; impossible inputs such as 2025-02-29 or 2026-04-31 return invalid_input. A successful API calculation costs $0.002 per item, while the browser experience can run the same pure calculation locally. Keep the original ISO date in source records if auditability matters, and store the returned quarter_start alongside week_number when downstream readers need the precise definition.
Using the result in reports and automation
A revenue dashboard can group snapshots by year, quarter, and week_number without allowing a week from the previous quarter to leak across the boundary. Scheduled exports can enrich every explicit reporting date with the returned quarter and quarter_start fields before loading a warehouse, making the grouping rule visible and reproducible. The result is also useful in tests: choose boundary dates around April 1, July 1, October 1, or January 1 and assert that week_number resets to one.
Integration use cases
Warehouse enrichment
Add year, quarter, quarter_start, and week_number fields to dated records before aggregation or historical replay.
Technical questions
What does the calculation cost?
The browser calculation is free. A successful API request costs $0.002 per item.