ISO Week Numbers 2028
2028 has 52 ISO 8601 weeks. Week 1 runs from 3 Jan to 9 Jan, and week 52 ends on 31 Dec. 1 January 2028 sits in week 52 of 2027 and 31 December 2028 in week 52 of 2028.
| Week | Monday | Sunday | Month | Falls in this week |
|---|---|---|---|---|
| 1 | 3 Jan | 9 Jan | January | |
| 2 | 10 Jan | 16 Jan | January | |
| 3 | 17 Jan | 23 Jan | January | |
| 4 | 24 Jan | 30 Jan | January | Chinese New Year |
| 5 | 31 Jan | 6 Feb | February | Groundhog Day |
| 6 | 7 Feb | 13 Feb | February | Super Bowl |
| 7 | 14 Feb | 20 Feb | February | Valentine's Day |
| 8 | 21 Feb | 27 Feb | February | |
| 9 | 28 Feb | 5 Mar | March | Mardi Gras, Spring, Leap Day |
| 10 | 6 Mar | 12 Mar | March | International Women's Day |
| 11 | 13 Mar | 19 Mar | March | St. Patrick's Day, Pi Day |
| 12 | 20 Mar | 26 Mar | March | the Spring Equinox, Earth Hour, World Water Day, the International Day of Happiness |
| 13 | 27 Mar | 2 Apr | March | April Fools' Day |
| 14 | 3 Apr | 9 Apr | April | World Health Day |
| 15 | 10 Apr | 16 Apr | April | Easter, Good Friday, Tax Day, National Pet Day |
| 16 | 17 Apr | 23 Apr | April | Earth Day, World Book Day |
| 17 | 24 Apr | 30 Apr | April | |
| 18 | 1 May | 7 May | May | Cinco de Mayo, Star Wars Day, May Day |
| 19 | 8 May | 14 May | May | Mother's Day |
| 20 | 15 May | 21 May | May | |
| 21 | 22 May | 28 May | May | |
| 22 | 29 May | 4 Jun | June | Summer, Memorial Day |
| 23 | 5 Jun | 11 Jun | June | World Environment Day, World Oceans Day |
| 24 | 12 Jun | 18 Jun | June | Father's Day |
| 25 | 19 Jun | 25 Jun | June | Juneteenth, the Summer Solstice |
| 26 | 26 Jun | 2 Jul | June | |
| 27 | 3 Jul | 9 Jul | July | Independence Day |
| 28 | 10 Jul | 16 Jul | July | |
| 29 | 17 Jul | 23 Jul | July | World Emoji Day |
| 30 | 24 Jul | 30 Jul | July | |
| 31 | 31 Jul | 6 Aug | August | |
| 32 | 7 Aug | 13 Aug | August | |
| 33 | 14 Aug | 20 Aug | August | Back to School, World Photography Day |
| 34 | 21 Aug | 27 Aug | August | National Dog Day |
| 35 | 28 Aug | 3 Sep | August | Autumn |
| 36 | 4 Sep | 10 Sep | September | Labor Day |
| 37 | 11 Sep | 17 Sep | September | |
| 38 | 18 Sep | 24 Sep | September | the Autumn Equinox, the International Day of Peace, Talk Like a Pirate Day |
| 39 | 25 Sep | 1 Oct | September | International Coffee Day, National Coffee Day |
| 40 | 2 Oct | 8 Oct | October | World Teachers' Day |
| 41 | 9 Oct | 15 Oct | October | Columbus Day, World Mental Health Day |
| 42 | 16 Oct | 22 Oct | October | Diwali, World Food Day |
| 43 | 23 Oct | 29 Oct | October | National Cat Day |
| 44 | 30 Oct | 5 Nov | November | Halloween |
| 45 | 6 Nov | 12 Nov | November | Veterans Day, Singles' Day |
| 46 | 13 Nov | 19 Nov | November | World Kindness Day, International Men's Day |
| 47 | 20 Nov | 26 Nov | November | Thanksgiving, Black Friday, World Television Day |
| 48 | 27 Nov | 3 Dec | November | Cyber Monday, Winter, Giving Tuesday |
| 49 | 4 Dec | 10 Dec | December | Human Rights Day |
| 50 | 11 Dec | 17 Dec | December | |
| 51 | 18 Dec | 24 Dec | December | the Winter Solstice |
| 52 | 25 Dec | 31 Dec | December | Christmas, New Year's Day, New Year's Eve, Boxing Day |
Why 2028 has 52 weeks
An ISO week year has 53 weeks when 1 January falls on a Thursday, or when the year is a leap year whose 1 January falls on a Wednesday. Every other year has 52. Because 52 weeks is only 364 days, the calendar has to absorb the leftover day or two somewhere, and a 53-week year is where it does that. Payroll systems, retail reporting and production planning all trip over this, because a 53-week year has one extra reporting period.
The year boundary
The first and last weeks of an ISO year rarely line up with the calendar year. Week 1 of 2028 starts on 3 Jan, and 1 January 2028 belongs to week 52 of 2027. This is not an error in the calendar: it follows directly from the rule that week 1 is the week containing the first Thursday, which keeps every week whole and every week in exactly one year.
Other years
The same calendar for 2020 to 2035. Years with 53 weeks are marked.
Frequently asked questions
How many weeks are in 2028?
2028 has 52 ISO 8601 weeks. A year has 53 weeks when it starts on a Thursday, or when it is a leap year starting on a Wednesday; otherwise it has 52.
Which week is 1 January 2028 in?
1 January 2028 falls in ISO week 52 of 2027. That is the previous ISO week year, because week 1 is the week containing the first Thursday, and in 2028 that week starts later.
Which week is 31 December 2028 in?
31 December 2028 falls in ISO week 52 of 2028.
When does an ISO week start?
On Monday. ISO 8601 defines the week as running Monday to Sunday, and week 1 as the week containing the first Thursday of the year, which is the same as the week containing 4 January. That is why an ISO week calendar can open in late December.
Need the week number for one specific date instead? Use the week number tool. Want this calendar as data? It is published as free JSON at /api/weeks/2028.json, documented on the data page.
Computed from the ISO 8601 rule, not from a stored table. Last updated 2026-08-05.
Related tools
Keep the date math going with the rest of the toolkit.