Week Numbers 2020
2020 has 53 numbered weeks under ISO 8601 and 53 under the US convention. Week 1 starts on Monday 30 December 2019 and week 53 ends on Sunday 3 January 2021.
Today in UTC.
Weeks run Monday to Sunday. Week 1 holds the first Thursday.
Week number now
of 53 in 2020 · ISO 8601 numbering
Saturday 4 January 2020 is in week 1 of 2020 under ISO 8601 numbering. That week runs from Monday 30 December 2019 to Sunday 5 January 2020.
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 | 2020-01-04 |
|---|---|
| Weekday | Saturday |
| ISO week 1 starts | 2019-12-30 |
| US week 1 starts | 2019-12-29 |
| This week runs | 2019-12-30 to 2020-01-05 |
| Weeks in 2020 | 53 weeks |
Every week of 2020
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 2019 | 5 January 2020 | 2019-12-30 to 2020-01-05 |
| Week 2 | 6 January 2020 | 12 January 2020 | 2020-01-06 to 2020-01-12 |
| Week 3 | 13 January 2020 | 19 January 2020 | 2020-01-13 to 2020-01-19 |
| Week 4 | 20 January 2020 | 26 January 2020 | 2020-01-20 to 2020-01-26 |
| Week 5 | 27 January 2020 | 2 February 2020 | 2020-01-27 to 2020-02-02 |
| Week 6 | 3 February 2020 | 9 February 2020 | 2020-02-03 to 2020-02-09 |
| Week 7 | 10 February 2020 | 16 February 2020 | 2020-02-10 to 2020-02-16 |
| Week 8 | 17 February 2020 | 23 February 2020 | 2020-02-17 to 2020-02-23 |
| Week 9 | 24 February 2020 | 1 March 2020 | 2020-02-24 to 2020-03-01 |
| Week 10 | 2 March 2020 | 8 March 2020 | 2020-03-02 to 2020-03-08 |
| Week 11 | 9 March 2020 | 15 March 2020 | 2020-03-09 to 2020-03-15 |
| Week 12 | 16 March 2020 | 22 March 2020 | 2020-03-16 to 2020-03-22 |
| Week 13 | 23 March 2020 | 29 March 2020 | 2020-03-23 to 2020-03-29 |
| Week 14 | 30 March 2020 | 5 April 2020 | 2020-03-30 to 2020-04-05 |
| Week 15 | 6 April 2020 | 12 April 2020 | 2020-04-06 to 2020-04-12 |
| Week 16 | 13 April 2020 | 19 April 2020 | 2020-04-13 to 2020-04-19 |
| Week 17 | 20 April 2020 | 26 April 2020 | 2020-04-20 to 2020-04-26 |
| Week 18 | 27 April 2020 | 3 May 2020 | 2020-04-27 to 2020-05-03 |
| Week 19 | 4 May 2020 | 10 May 2020 | 2020-05-04 to 2020-05-10 |
| Week 20 | 11 May 2020 | 17 May 2020 | 2020-05-11 to 2020-05-17 |
| Week 21 | 18 May 2020 | 24 May 2020 | 2020-05-18 to 2020-05-24 |
| Week 22 | 25 May 2020 | 31 May 2020 | 2020-05-25 to 2020-05-31 |
| Week 23 | 1 June 2020 | 7 June 2020 | 2020-06-01 to 2020-06-07 |
| Week 24 | 8 June 2020 | 14 June 2020 | 2020-06-08 to 2020-06-14 |
| Week 25 | 15 June 2020 | 21 June 2020 | 2020-06-15 to 2020-06-21 |
| Week 26 | 22 June 2020 | 28 June 2020 | 2020-06-22 to 2020-06-28 |
| Week 27 | 29 June 2020 | 5 July 2020 | 2020-06-29 to 2020-07-05 |
| Week 28 | 6 July 2020 | 12 July 2020 | 2020-07-06 to 2020-07-12 |
| Week 29 | 13 July 2020 | 19 July 2020 | 2020-07-13 to 2020-07-19 |
| Week 30 | 20 July 2020 | 26 July 2020 | 2020-07-20 to 2020-07-26 |
| Week 31 | 27 July 2020 | 2 August 2020 | 2020-07-27 to 2020-08-02 |
| Week 32 | 3 August 2020 | 9 August 2020 | 2020-08-03 to 2020-08-09 |
| Week 33 | 10 August 2020 | 16 August 2020 | 2020-08-10 to 2020-08-16 |
| Week 34 | 17 August 2020 | 23 August 2020 | 2020-08-17 to 2020-08-23 |
| Week 35 | 24 August 2020 | 30 August 2020 | 2020-08-24 to 2020-08-30 |
| Week 36 | 31 August 2020 | 6 September 2020 | 2020-08-31 to 2020-09-06 |
| Week 37 | 7 September 2020 | 13 September 2020 | 2020-09-07 to 2020-09-13 |
| Week 38 | 14 September 2020 | 20 September 2020 | 2020-09-14 to 2020-09-20 |
| Week 39 | 21 September 2020 | 27 September 2020 | 2020-09-21 to 2020-09-27 |
| Week 40 | 28 September 2020 | 4 October 2020 | 2020-09-28 to 2020-10-04 |
| Week 41 | 5 October 2020 | 11 October 2020 | 2020-10-05 to 2020-10-11 |
| Week 42 | 12 October 2020 | 18 October 2020 | 2020-10-12 to 2020-10-18 |
| Week 43 | 19 October 2020 | 25 October 2020 | 2020-10-19 to 2020-10-25 |
| Week 44 | 26 October 2020 | 1 November 2020 | 2020-10-26 to 2020-11-01 |
| Week 45 | 2 November 2020 | 8 November 2020 | 2020-11-02 to 2020-11-08 |
| Week 46 | 9 November 2020 | 15 November 2020 | 2020-11-09 to 2020-11-15 |
| Week 47 | 16 November 2020 | 22 November 2020 | 2020-11-16 to 2020-11-22 |
| Week 48 | 23 November 2020 | 29 November 2020 | 2020-11-23 to 2020-11-29 |
| Week 49 | 30 November 2020 | 6 December 2020 | 2020-11-30 to 2020-12-06 |
| Week 50 | 7 December 2020 | 13 December 2020 | 2020-12-07 to 2020-12-13 |
| Week 51 | 14 December 2020 | 20 December 2020 | 2020-12-14 to 2020-12-20 |
| Week 52 | 21 December 2020 | 27 December 2020 | 2020-12-21 to 2020-12-27 |
| Week 53 | 28 December 2020 | 3 January 2021 | 2020-12-28 to 2021-01-03 |
2020 at a glance
| ISO 8601 weeks | 53 |
|---|---|
| US weeks | 53 |
| Days in the year | 366 |
| Leap year | Yes |
| 1 January falls on | Wednesday |
| 31 December falls on | Thursday |
Why the first week can start in December
Week 1 of 2020 starts on Monday 30 December 2019. 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 2020 can fall in week 1 of 2021. 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 2020?
53 under ISO 8601 numbering, and 53 under the US convention. 2020 is a leap year of 366 days, which is 52 weeks and two days over.
When does week 1 of 2020 start?
Monday 30 December 2019 under ISO 8601, which runs Monday to Sunday. Under the US convention it starts on Sunday 29 December 2019. Both can begin in the previous December, which is normal.
Does 2020 have 53 weeks?
Yes, under ISO 8601. A year has 53 numbered weeks when it starts on a Thursday, or on a Wednesday in a leap year. 1 January 2020 is a Wednesday.