Week Numbers 2025
2025 has 52 numbered weeks under ISO 8601 and 53 under the US convention. Week 1 starts on Monday 30 December 2024 and week 52 ends on Sunday 28 December 2025.
Today in UTC.
Weeks run Monday to Sunday. Week 1 holds the first Thursday.
Week number now
of 52 in 2025 · ISO 8601 numbering
Saturday 4 January 2025 is in week 1 of 2025 under ISO 8601 numbering. That week runs from Monday 30 December 2024 to Sunday 5 January 2025.
Both conventions agree on this date: week 1 either way. They part company for most of January and often at the end of December.
Show the working
| Date | 2025-01-04 |
|---|---|
| Weekday | Saturday |
| ISO week 1 starts | 2024-12-30 |
| US week 1 starts | 2024-12-29 |
| This week runs | 2024-12-30 to 2025-01-05 |
| Weeks in 2025 | 52 weeks |
Every week of 2025
ISO 8601 weeks, running Monday to Sunday. Week 1 is the week holding the first Thursday of the year, which is why it can start in the previous December.
| Week | Starts | Ends | ISO dates |
|---|---|---|---|
| Week 1 | 30 December 2024 | 5 January 2025 | 2024-12-30 to 2025-01-05 |
| Week 2 | 6 January 2025 | 12 January 2025 | 2025-01-06 to 2025-01-12 |
| Week 3 | 13 January 2025 | 19 January 2025 | 2025-01-13 to 2025-01-19 |
| Week 4 | 20 January 2025 | 26 January 2025 | 2025-01-20 to 2025-01-26 |
| Week 5 | 27 January 2025 | 2 February 2025 | 2025-01-27 to 2025-02-02 |
| Week 6 | 3 February 2025 | 9 February 2025 | 2025-02-03 to 2025-02-09 |
| Week 7 | 10 February 2025 | 16 February 2025 | 2025-02-10 to 2025-02-16 |
| Week 8 | 17 February 2025 | 23 February 2025 | 2025-02-17 to 2025-02-23 |
| Week 9 | 24 February 2025 | 2 March 2025 | 2025-02-24 to 2025-03-02 |
| Week 10 | 3 March 2025 | 9 March 2025 | 2025-03-03 to 2025-03-09 |
| Week 11 | 10 March 2025 | 16 March 2025 | 2025-03-10 to 2025-03-16 |
| Week 12 | 17 March 2025 | 23 March 2025 | 2025-03-17 to 2025-03-23 |
| Week 13 | 24 March 2025 | 30 March 2025 | 2025-03-24 to 2025-03-30 |
| Week 14 | 31 March 2025 | 6 April 2025 | 2025-03-31 to 2025-04-06 |
| Week 15 | 7 April 2025 | 13 April 2025 | 2025-04-07 to 2025-04-13 |
| Week 16 | 14 April 2025 | 20 April 2025 | 2025-04-14 to 2025-04-20 |
| Week 17 | 21 April 2025 | 27 April 2025 | 2025-04-21 to 2025-04-27 |
| Week 18 | 28 April 2025 | 4 May 2025 | 2025-04-28 to 2025-05-04 |
| Week 19 | 5 May 2025 | 11 May 2025 | 2025-05-05 to 2025-05-11 |
| Week 20 | 12 May 2025 | 18 May 2025 | 2025-05-12 to 2025-05-18 |
| Week 21 | 19 May 2025 | 25 May 2025 | 2025-05-19 to 2025-05-25 |
| Week 22 | 26 May 2025 | 1 June 2025 | 2025-05-26 to 2025-06-01 |
| Week 23 | 2 June 2025 | 8 June 2025 | 2025-06-02 to 2025-06-08 |
| Week 24 | 9 June 2025 | 15 June 2025 | 2025-06-09 to 2025-06-15 |
| Week 25 | 16 June 2025 | 22 June 2025 | 2025-06-16 to 2025-06-22 |
| Week 26 | 23 June 2025 | 29 June 2025 | 2025-06-23 to 2025-06-29 |
| Week 27 | 30 June 2025 | 6 July 2025 | 2025-06-30 to 2025-07-06 |
| Week 28 | 7 July 2025 | 13 July 2025 | 2025-07-07 to 2025-07-13 |
| Week 29 | 14 July 2025 | 20 July 2025 | 2025-07-14 to 2025-07-20 |
| Week 30 | 21 July 2025 | 27 July 2025 | 2025-07-21 to 2025-07-27 |
| Week 31 | 28 July 2025 | 3 August 2025 | 2025-07-28 to 2025-08-03 |
| Week 32 | 4 August 2025 | 10 August 2025 | 2025-08-04 to 2025-08-10 |
| Week 33 | 11 August 2025 | 17 August 2025 | 2025-08-11 to 2025-08-17 |
| Week 34 | 18 August 2025 | 24 August 2025 | 2025-08-18 to 2025-08-24 |
| Week 35 | 25 August 2025 | 31 August 2025 | 2025-08-25 to 2025-08-31 |
| Week 36 | 1 September 2025 | 7 September 2025 | 2025-09-01 to 2025-09-07 |
| Week 37 | 8 September 2025 | 14 September 2025 | 2025-09-08 to 2025-09-14 |
| Week 38 | 15 September 2025 | 21 September 2025 | 2025-09-15 to 2025-09-21 |
| Week 39 | 22 September 2025 | 28 September 2025 | 2025-09-22 to 2025-09-28 |
| Week 40 | 29 September 2025 | 5 October 2025 | 2025-09-29 to 2025-10-05 |
| Week 41 | 6 October 2025 | 12 October 2025 | 2025-10-06 to 2025-10-12 |
| Week 42 | 13 October 2025 | 19 October 2025 | 2025-10-13 to 2025-10-19 |
| Week 43 | 20 October 2025 | 26 October 2025 | 2025-10-20 to 2025-10-26 |
| Week 44 | 27 October 2025 | 2 November 2025 | 2025-10-27 to 2025-11-02 |
| Week 45 | 3 November 2025 | 9 November 2025 | 2025-11-03 to 2025-11-09 |
| Week 46 | 10 November 2025 | 16 November 2025 | 2025-11-10 to 2025-11-16 |
| Week 47 | 17 November 2025 | 23 November 2025 | 2025-11-17 to 2025-11-23 |
| Week 48 | 24 November 2025 | 30 November 2025 | 2025-11-24 to 2025-11-30 |
| Week 49 | 1 December 2025 | 7 December 2025 | 2025-12-01 to 2025-12-07 |
| Week 50 | 8 December 2025 | 14 December 2025 | 2025-12-08 to 2025-12-14 |
| Week 51 | 15 December 2025 | 21 December 2025 | 2025-12-15 to 2025-12-21 |
| Week 52 | 22 December 2025 | 28 December 2025 | 2025-12-22 to 2025-12-28 |
2025 at a glance
| ISO 8601 weeks | 52 |
|---|---|
| US weeks | 53 |
| Days in the year | 365 |
| Leap year | No |
| 1 January falls on | Wednesday |
| 31 December falls on | Wednesday |
Why the first week can start in December
Week 1 of 2025 starts on Monday 30 December 2024. If that date is in December it is not a mistake. ISO 8601 assigns a whole week to the year holding most of its days, so a week straddling New Year belongs to one year or the other rather than being split in half.
The same rule at the other end means the last days of 2025 can fall in week 1 of 2026. Both are correct, and both are shown by the tool above when you enter a date near the boundary.
Frequently asked questions
How many weeks are in 2025?
52 under ISO 8601 numbering, and 53 under the US convention. 2025 is a common year of 365 days, which is 52 weeks and one day over.
When does week 1 of 2025 start?
Monday 30 December 2024 under ISO 8601, which runs Monday to Sunday. Under the US convention it starts on Sunday 29 December 2024. Both can begin in the previous December, which is normal.
Does 2025 have 53 weeks?
No. 2025 has 52 ISO weeks. A year only has 53 when it starts on a Thursday, or on a Wednesday in a leap year, and 1 January 2025 is a Wednesday.