Week 1 of the year
When is week 1? The exact Monday–Sunday dates of ISO week 1 for every year from 2024 to 2032.
Week 1 of 2026 runs from Monday, Dec 29, 2025 to Sunday, Jan 4, 2026 (Dec / Jan). Week 1 of 2026 has already passed (28 weeks ago). ISO week code: 2026-W01.
Week 1 dates by year
| Year | Week 1 starts (Mon) | Week 1 ends (Sun) | Month |
|---|---|---|---|
| 2024 | Monday, January 1, 2024 | Sunday, January 7, 2024 | January |
| 2025 | Monday, December 30, 2024 | Sunday, January 5, 2025 | Dec / Jan |
| 2026 | Monday, December 29, 2025 | Sunday, January 4, 2026 | Dec / Jan |
| 2027 | Monday, January 4, 2027 | Sunday, January 10, 2027 | January |
| 2028 | Monday, January 3, 2028 | Sunday, January 9, 2028 | January |
| 2029 | Monday, January 1, 2029 | Sunday, January 7, 2029 | January |
| 2030 | Monday, December 31, 2029 | Sunday, January 6, 2030 | Dec / Jan |
| 2031 | Monday, December 30, 2030 | Sunday, January 5, 2031 | Dec / Jan |
| 2032 | Monday, December 29, 2031 | Sunday, January 4, 2032 | Dec / Jan |
All weeks
Frequently asked questions
What month is week 1 in?
Week 1 typically falls in January. The exact dates shift by up to a few days from year to year because week 1 is anchored to January 4, not January 1.
How do I write week 1 as a week code?
The ISO code is the year plus W01 — for example 2026-W01, short form 26W01, or YYWW date code 2601. See week number formats.
Are these dates the same in every country?
Yes for ISO 8601 (Monday-start) numbering, which is what this table shows. US Sunday-start calendars can label the same days with a number one higher — see week start conventions.