ISO week dates
When Is Week 51? Dates & Calendar
Today: · Eastern Time (America/New_York)
Week 51 dates
Week 51 of 2026
Week 51 of 2026 runs from Monday, December 14, 2026 through Sunday, December 20, 2026.
- Relevant ISO year
- 2026
- Weeks in this ISO year
- 53
- Today’s ISO week / year
- 43 / 2026
Week 51 of 2026
Each of the seven selected dates is labeled Week 51.
December 2026
| Mon | Tue | Wed | Thu | Fri | Sat | Sun |
|---|---|---|---|---|---|---|
| Week 51 | Week 51 | Week 51 | Week 51 | Week 51 | Week 51 | Week 51 |
Week 51 by ISO year
| ISO year | Monday — start | Sunday — end |
|---|---|---|
| 2024 | Mon, Dec 16, 2024 | Sun, Dec 22, 2024 |
| 2025 | Mon, Dec 15, 2025 | Sun, Dec 21, 2025 |
| 2026 | Mon, Dec 14, 2026 | Sun, Dec 20, 2026 |
| 2027 | Mon, Dec 20, 2027 | Sun, Dec 26, 2027 |
| 2028 | Mon, Dec 18, 2028 | Sun, Dec 24, 2028 |
| 2029 | Mon, Dec 17, 2029 | Sun, Dec 23, 2029 |
| 2030 | Mon, Dec 16, 2030 | Sun, Dec 22, 2030 |
| 2031 | Mon, Dec 15, 2031 | Sun, Dec 21, 2031 |
| 2032 | Mon, Dec 13, 2032 | Sun, Dec 19, 2032 |
| 2033 | Mon, Dec 19, 2033 | Sun, Dec 25, 2033 |
| 2034 | Mon, Dec 18, 2034 | Sun, Dec 24, 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.