What week number is it?
Today’s week, any date’s week, every week of the year.
Today
ISO 8601: weeks run Monday to Sunday and week 1 is the week with the year’s first Thursday, so 1–3 January can fall in the last week of the year before. A year has 52 or 53 weeks.
“Week of the month” is used two ways: the nth time the weekday comes round in the month (the 2nd Tuesday is always between the 8th and the 14th), or the row the day is on in a month calendar. Both are shown.
Find the week of a date
Find the dates of a week
All weeks of
Nothing leaves your device
This tool runs entirely in your browser. What you type, play or record here stays on your device: nothing is uploaded or saved on a server.
Example
Example: Thanksgiving 2027 is week 47 in Europe and week 48 in the US
A US team plans the 2027 holiday weeks with a European office that counts ISO weeks. Each date goes into “Find the week of a date”, read once with ISO 8601 and once with the US count; the page also gives the week of the month.
- Thursday, November 25, 2027: ISO week 47, Monday, November 22 to Sunday, November 28; US week 48, Sunday, November 21 to Saturday, November 27.
- Week of the month: “The 4th Thursday of November (also the last Thursday of the month)”, which is how Thanksgiving is set.
- Memorial Day, Monday, May 31, 2027, shows as the 5th Monday of May and also the last: ISO week 22, US week 23.
| Date (2027) | Holiday | ISO week | US week | Week of the month |
|---|---|---|---|---|
| Mon, January 18 | Martin Luther King Jr. Day | 3 | 4 | 3rd Monday |
| Mon, February 15 | Presidents’ Day | 7 | 8 | 3rd Monday |
| Mon, May 31 | Memorial Day | 22 | 23 | 5th and last Monday |
| Sun, July 4 | Independence Day | 26 | 28 | 1st Sunday |
| Mon, September 6 | Labor Day | 36 | 37 | 1st Monday |
| Thu, November 25 | Thanksgiving | 47 | 48 | 4th and last Thursday |
| Sat, December 25 | Christmas Day | 51 | 52 | 4th and last Saturday |
| Fri, December 31 | New Year’s Eve | 52 | 1 (of 2028) | 5th and last Friday |
In 2027 a Monday-to-Saturday date is one week higher in the US count than in ISO, and a Sunday two, because a US week starts on the Sunday an ISO week ends on. Both counts give 2027 52 weeks; ISO week 1 runs from Monday, January 4 to Sunday, January 10.
How it works
- Open the page: today’s week number shows at once, with the Monday and Sunday of the week.
- Type a date to find its week, or a year and week number to find its dates.
- Scroll the list of all weeks of the year; switch to the US count if you need weeks starting on Sunday.
Frequently asked questions
- How are week numbers counted?
- Most of the world uses ISO 8601: weeks start on Monday and week 1 is the week with the year’s first Thursday — always the week of 4 January. 30 September 2026, for example, is in week 40.
- Why is 1 January sometimes in week 53?
- Because the week belongs to the year its Thursday falls in: 1–3 January 2027 are in week 53 of 2026, and 30 December 2024 was already in week 1 of 2025.
- Which years have 53 weeks?
- Years that start on a Thursday, or leap years that start on a Wednesday: 2020, 2026, 2032 and 2037, for example.
- What is the US week number?
- In the US weeks run Sunday to Saturday and week 1 is the one with 1 January. In a year that starts on a Friday or a Saturday, such as 2027, the US number is one higher from Monday to Saturday and two higher on a Sunday; in other years, such as 2026, the two match from Monday to Saturday and a Sunday is one higher. Around New Year the two counts can also put a day in different years, and spreadsheet week functions differ again there.
- What week is Thanksgiving 2027?
- Thursday, November 25, 2027 is in ISO week 47 (November 22–28) and in US week 48 (November 21–27). Thanksgiving is the 4th Thursday of November, which the page shows under the week of the month.
- Why do the US and ISO numbers differ by two on a Sunday?
- A US week starts on Sunday and an ISO week ends on one. In 2027, US week 1 runs from December 27, 2026 to January 2, 2027, so Monday to Saturday are one week higher in the US count and a Sunday two: July 4, 2027 is ISO week 26 and US week 28.
- Is anything saved?
- No. It is worked out in your browser from your device’s date.