📅 Week Number Reference 2025
ISO 8601 week numbers for 2025. Weeks run Monday through Sunday. Week 1 is the week containing the first Thursday of January (and therefore January 4th).
Note: All dates are in 2025 unless otherwise noted. End dates shown are Sunday.
| Week # | Monday (Start) | Sunday (End) |
|---|---|---|
| W01 | Dec 30, 2024 | Jan 5 |
| W02 | Jan 6 | Jan 12 |
| W03 | Jan 13 | Jan 19 |
| W04 | Jan 20 | Jan 26 |
| W05 | Jan 27 | Feb 2 |
| W06 | Feb 3 | Feb 9 |
| W07 | Feb 10 | Feb 16 |
| W08 | Feb 17 | Feb 23 |
| W09 | Feb 24 | Mar 2 |
| W10 | Mar 3 | Mar 9 |
| W11 | Mar 10 | Mar 16 |
| W12 | Mar 17 | Mar 23 |
| W13 | Mar 24 | Mar 30 |
| W14 | Mar 31 | Apr 6 |
| W15 | Apr 7 | Apr 13 |
| W16 | Apr 14 | Apr 20 |
| W17 | Apr 21 | Apr 27 |
| W18 | Apr 28 | May 4 |
| W19 | May 5 | May 11 |
| W20 | May 12 | May 18 |
| W21 | May 19 | May 25 |
| W22 | May 26 | Jun 1 |
| W23 | Jun 2 | Jun 8 |
| W24 | Jun 9 | Jun 15 |
| W25 | Jun 16 | Jun 22 |
| W26 | Jun 23 | Jun 29 |
| W27 | Jun 30 | Jul 6 |
| W28 | Jul 7 | Jul 13 |
| W29 | Jul 14 | Jul 20 |
| W30 | Jul 21 | Jul 27 |
| W31 | Jul 28 | Aug 3 |
| W32 | Aug 4 | Aug 10 |
| W33 | Aug 11 | Aug 17 |
| W34 | Aug 18 | Aug 24 |
| W35 | Aug 25 | Aug 31 |
| W36 | Sep 1 | Sep 7 |
| W37 | Sep 8 | Sep 14 |
| W38 | Sep 15 | Sep 21 |
| W39 | Sep 22 | Sep 28 |
| W40 | Sep 29 | Oct 5 |
| W41 | Oct 6 | Oct 12 |
| W42 | Oct 13 | Oct 19 |
| W43 | Oct 20 | Oct 26 |
| W44 | Oct 27 | Nov 2 |
| W45 | Nov 3 | Nov 9 |
| W46 | Nov 10 | Nov 16 |
| W47 | Nov 17 | Nov 23 |
| W48 | Nov 24 | Nov 30 |
| W49 | Dec 1 | Dec 7 |
| W50 | Dec 8 | Dec 14 |
| W51 | Dec 15 | Dec 21 |
| W52 | Dec 22 | Dec 28 |
How ISO Week Numbers Work
The ISO 8601 standard defines Week 1 as the week containing the first Thursday of the year. This means January 1 may fall in Week 52 or 53 of the previous year, and December 31 may fall in Week 1 of the next year.
Most years have 52 weeks. Years where January 1 is Thursday, or leap years where January 1 is Wednesday or Thursday, have 53 weeks. 2025 has 52 ISO weeks.