The 53 weeks of 2026, each with the dates it runs from and to.
Weeks start on Sunday, and week 1 is the one containing 1 January (US convention).
| Week | Dates |
|---|---|
| 1 | Dec 28 – Jan 3 |
| 2 | Jan 4 – Jan 10 |
| 3 | Jan 11 – Jan 17 |
| 4 | Jan 18 – Jan 24 |
| 5 | Jan 25 – Jan 31 |
| 6 | Feb 1 – Feb 7 |
| 7 | Feb 8 – Feb 14 |
| 8 | Feb 15 – Feb 21 |
| 9 | Feb 22 – Feb 28 |
| 10 | Mar 1 – Mar 7 |
| 11 | Mar 8 – Mar 14 |
| 12 | Mar 15 – Mar 21 |
| 13 | Mar 22 – Mar 28 |
| 14 | Mar 29 – Apr 4 |
| 15 | Apr 5 – Apr 11 |
| 16 | Apr 12 – Apr 18 |
| 17 | Apr 19 – Apr 25 |
| 18 | Apr 26 – May 2 |
| 19 | May 3 – May 9 |
| 20 | May 10 – May 16 |
| 21 | May 17 – May 23 |
| 22 | May 24 – May 30 |
| 23 | May 31 – Jun 6 |
| 24 | Jun 7 – Jun 13 |
| 25 | Jun 14 – Jun 20 |
| 26 | Jun 21 – Jun 27 |
| 27 | Jun 28 – Jul 4 |
| 28 | Jul 5 – Jul 11 |
| 29 | Jul 12 – Jul 18 |
| 30 | Jul 19 – Jul 25 |
| 31 | Jul 26 – Aug 1 |
| 32 | Aug 2 – Aug 8 |
| 33 | Aug 9 – Aug 15 |
| 34 | Aug 16 – Aug 22 |
| 35 | Aug 23 – Aug 29 |
| 36 | Aug 30 – Sep 5 |
| 37 | Sep 6 – Sep 12 |
| 38 | Sep 13 – Sep 19 |
| 39 | Sep 20 – Sep 26 |
| 40 | Sep 27 – Oct 3 |
| 41 | Oct 4 – Oct 10 |
| 42 | Oct 11 – Oct 17 |
| 43 | Oct 18 – Oct 24 |
| 44 | Oct 25 – Oct 31 |
| 45 | Nov 1 – Nov 7 |
| 46 | Nov 8 – Nov 14 |
| 47 | Nov 15 – Nov 21 |
| 48 | Nov 22 – Nov 28 |
| 49 | Nov 29 – Dec 5 |
| 50 | Dec 6 – Dec 12 |
| 51 | Dec 13 – Dec 19 |
| 52 | Dec 20 – Dec 26 |
| 53 | Dec 27 – Jan 2 |
Weeks here start on Sunday and week 1 is the one containing 1 January, which is the convention used in the United States. Most of Europe uses ISO-8601 instead: weeks run Monday to Sunday, and week 1 is the one containing the first Thursday of the year. The two give different numbers for much of the year, so a week number is only unambiguous once you know which system produced it.
Under ISO-8601 the year boundary does not align with the week boundary. When 1 January falls on a Friday, Saturday or Sunday, those days belong to the last week of the previous year — which is why a week number always travels with a year, and why «week 53» on its own is ambiguous.
Week numbers are administrative rather than astronomical. They appear in contracts, delivery schedules, shift rotas and production planning, and they exist so that two parties can name a stretch of seven days without spelling out both dates.
2026 has 52 weeks, which is the ordinary case.
The US convention: weeks start on Sunday, and week 1 is the one containing 1 January. The Portuguese, Spanish, German and French versions of this page use ISO-8601 instead, because that is the standard in those markets.
Because 52 weeks are 364 days, one short of a year. The extra day accumulates, and roughly every five or six years it adds up to a whole extra week. Under ISO-8601 it happens when the year begins on a Thursday, or on a Wednesday in a leap year.
A week belongs to exactly one year, but not always the one its days suggest. Under ISO-8601, 1 January 2027 falls on a Friday and belongs to week 53 of 2026 — the first three days of the calendar year are part of the previous week-year.
They are the same thing under different names. German uses Kalenderwoche, abbreviated KW, and it appears routinely in contracts and delivery dates. English speakers say week number, and use it far less often in everyday business.
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