2028 has 52 ISO weeks
2028 contains 52 ISO weeks. Week 1 opens on Monday, January 3, 2028 and week 52 closes on Sunday, December 31, 2028. That is 364 days of week numbering laid over a calendar year of 366 days, which is why the first and last weeks reach outside 2028 itself.
How many weeks are in 2028?
52. A year holds 52 whole weeks and one spare day, or two spare days in a leap year, so most years number 52 weeks and the spare days are absorbed by the weeks at either end. A year gets a 53rd week when those spare days line up so that a full extra Monday-to-Sunday block belongs to it. The test is short: a year has 53 ISO weeks when 1 January is a Thursday, or when it is a leap year beginning on a Wednesday. 1 January 2028 is a Saturday and the year is a leap year, but a leap year only qualifies when it starts on a Wednesday, so 2028 stops at 52 weeks. The next 53-week year is 2032.
Why the count is not simply 365 divided by 7
Dividing 366 by seven gives 52.286, which is not a whole number, so week boundaries cannot line up with year boundaries. ISO 8601 resolves this by numbering complete weeks and assigning each one to the year that holds most of its days, which is the same as the rule that week 1 is the week containing the first Thursday. The consequence is visible at both ends of 2028: week 1 runs January 3 to January 9, entirely inside the year, and week 52 runs December 25 to December 31, entirely inside the year.
Week counts for nearby years
| Year | 1 January | Leap year | ISO weeks |
|---|---|---|---|
| 2025 | Wednesday | no | 52 |
| 2026 | Thursday | no | 53 |
| 2027 | Friday | no | 52 |
| 2028 | Saturday | yes | 52 |
| 2029 | Monday | no | 52 |
| 2030 | Tuesday | no | 52 |
| 2031 | Wednesday | no | 52 |
| 2032 | Thursday | yes | 53 |
Long years are rare and unevenly spaced. Counting every year in a full 400-year Gregorian cycle gives 71 years with 53 weeks out of 400, which works out at roughly one year in 5.6. The gaps between them run to five, six or eleven years rather than repeating on a fixed interval, which is why payroll and retail calendars that use 52-week or 53-week years have to be checked rather than assumed.
The first and last weeks of 2028
| Week | Monday | Sunday | Spans a year end |
|---|---|---|---|
| Week 1 | January 3, 2028 | January 9, 2028 | no |
| Week 52 | December 25, 2028 | December 31, 2028 | no |
Questions
- How many weeks are in 2028?
- 52 ISO weeks, running from January 3, 2028 to December 31, 2028.
- Does 2028 have a week 53?
- No, 2028 stops at week 52. The next 53-week year is 2032.
- Which week does 1 January 2028 fall in?
- Week 52 of 2027. 1 January 2028 is a Saturday.
- How many days are in 2028?
- 366, because 2028 is a leap year.
Browse the weeks
Other years
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