Week 4 of 2026 runs January 19 to January 25
ISO week 4 of 2026 begins on Monday, January 19, 2026 and ends on Sunday, January 25, 2026. It has already passed; the current week is 39. The week covers January only.
What dates are in week 4?
| Weekday | Date | Day of year | Notes |
|---|---|---|---|
| Monday | January 19, 2026 | 19 | Martin Luther King Jr. Day |
| Tuesday | January 20, 2026 | 20 | |
| Wednesday | January 21, 2026 | 21 | |
| Thursday | January 22, 2026 | 22 | |
| Friday | January 23, 2026 | 23 | |
| Saturday | January 24, 2026 | 24 | |
| Sunday | January 25, 2026 | 25 |
Week 4 of 2026 contains Martin Luther King Jr. Day on January 19. The seven dates always run Monday through Sunday, which is the part of ISO 8601 that most often catches people out: a week that starts on Sunday is a different convention and gives a different number.
How ISO week 4 is worked out
ISO 8601 fixes week one as the week containing the first Thursday of January, which is the same as saying the week containing 4 January, or the week holding the majority of its days in the new year. Counting forward from there, week 4 is the 4th Monday-to-Sunday block of 2026, which lands on January 19. All seven dates sit inside 2026, so the ISO year and the calendar year agree for this week.
When is week 4 in other years?
| Year | Monday | Sunday | Weeks in year |
|---|---|---|---|
| 2026 | January 19 | January 25 | 53 |
| 2027 | January 25 | January 31 | 52 |
| 2028 | January 24 | January 30 | 52 |
| 2029 | January 22 | January 28 | 52 |
| 2030 | January 21 | January 27 | 52 |
Week 4 shifts by a day or two each year because a year is 52 weeks plus one or two days, so the Monday that opens it moves from January 19 in 2026 to January 25 in 2027.
How far away is week 4?
Today is Wednesday, September 23, 2026, which sits in ISO week 39 of 2026. Week 4 of 2026 closed 241 days ago. The same week number in the following year is listed in the table above.
Questions
- What dates are in week 4 of 2026?
- Monday January 19, 2026 through Sunday January 25, 2026.
- What week is it now?
- ISO week 39 of 2026. Today is Wednesday, September 23, 2026.
- How many weeks does 2026 have?
- 53. The 2026 week count page explains the rule.
- Do ISO weeks start on Monday or Sunday?
- Monday. A Sunday-first week is a different convention and can give a different week number for the same date.
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