ISO week dates
When Is Week 4? Dates & Calendar
Today: · Eastern Time (America/New_York)
Week 4 dates
Week 4 of 2026
Week 4 of 2026 runs from Monday, January 19, 2026 through Sunday, January 25, 2026.
- Relevant ISO year
- 2026
- Weeks in this ISO year
- 53
- Today’s ISO week / year
- 43 / 2026
Week 4 of 2026
Each of the seven selected dates is labeled Week 4.
January 2026
| Mon | Tue | Wed | Thu | Fri | Sat | Sun |
|---|---|---|---|---|---|---|
| Week 4 | Week 4 | Week 4 | Week 4 | Week 4 | Week 4 | Week 4 |
Week 4 by ISO year
| ISO year | Monday — start | Sunday — end |
|---|---|---|
| 2024 | Mon, Jan 22, 2024 | Sun, Jan 28, 2024 |
| 2025 | Mon, Jan 20, 2025 | Sun, Jan 26, 2025 |
| 2026 | Mon, Jan 19, 2026 | Sun, Jan 25, 2026 |
| 2027 | Mon, Jan 25, 2027 | Sun, Jan 31, 2027 |
| 2028 | Mon, Jan 24, 2028 | Sun, Jan 30, 2028 |
| 2029 | Mon, Jan 22, 2029 | Sun, Jan 28, 2029 |
| 2030 | Mon, Jan 21, 2030 | Sun, Jan 27, 2030 |
| 2031 | Mon, Jan 20, 2031 | Sun, Jan 26, 2031 |
| 2032 | Mon, Jan 19, 2032 | Sun, Jan 25, 2032 |
| 2033 | Mon, Jan 24, 2033 | Sun, Jan 30, 2033 |
| 2034 | Mon, Jan 23, 2034 | Sun, Jan 29, 2034 |
Quick answers
- How many weeks are in 2026?
- 2026 has 53 ISO weeks. Week 53 does not occur every year.
- What week is it today?
- Today is in ISO week 43 of 2026.
How this is calculated
- ISO weeks run Monday through Sunday. Week 1 contains January 4 (the first Thursday of the year).
- The relevant year is the ISO week-year of today in Eastern Time (America/New_York). Near New Year, it can differ from the calendar year.
- An ISO year has 52 or 53 weeks. Week 53 exists only in applicable ISO years; it is never rolled into Week 1.