Week Numbers 2025
How many ISO weeks are in 2025?
Answer
2025 ended on Wednesday, December 31, 2025. Its last ISO week, week 52, ran until Sunday, December 28, 2025.
All 52 ISO weeks of 2025
| Week | Monday | Sunday |
|---|---|---|
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| 51 | ||
| 52 |
ISO weeks are always whole, Monday to Sunday, so the numbering of 2025 starts on Monday, December 30, 2024, and ends on Sunday, December 28, 2025. To see these weeks inside the months, open the 2025 calendar with week numbers.
Why 2025 has 52 ISO weeks
2025 starts on Wednesday, January 1, 2025, and ends on Wednesday, December 31, 2025; it is a common year of 365 days. Neither condition holds, so it has 52 numbered weeks. Week 1 is the week that contains the first Thursday of the year, January 2, 2025.
Counted as whole blocks of seven days inside the calendar year, 2025 is 365 = 52 × 7 + 1, that is 52 weeks and 1 day. Both are true: the numbered ISO weeks are whole, so the first and the last of them may borrow days from the neighbouring years.
In the US numbering (weeks from Sunday, week 1 is the week that contains January 1) 2025 has 52 weeks, and week 1 starts on Sunday, December 29, 2024.
Related Calculations
See Also
- Date Calculator - Add to or Subtract Days/Weeks/Months or Years from Today
- Weeks and Days Ago From Today - Calculate what day was it Weeks and Days Ago From Today
- Days Between Two Dates - Calculate the Difference Between Two Dates. How many days, months, and years are between two dates? From date to date calculator
- Days until Date - How many days, weeks, months and years until a Date. How Many Days Until My Birthday? Countdown to date
- Calendar by Month and Year - A month or a whole year laid out by weekday, with ISO week numbers and holidays
- How Many Weeks Are in a Year - Days, weeks, months, hours, minutes and seconds in a named year, leap years included
- What Day of the Week Is It - Find the day of the week of any date. What day of week was or will be a date
- What Day of the Year Is It - Today's day number, the days and weeks left until the end of the year and the share of it already gone
<a href="https://calculat.io/en/date/week-number/2025">Week Numbers 2025: All 52 ISO Weeks with Dates - Calculatio</a>
ISO Weeks in Nearby Years
| Year | ISO weeks | Week 1 starts | Last week ends |
|---|---|---|---|
| 2020 | 53 | Dec 30, 2019 | Jan 3, 2021 |
| 2021 | 52 | Jan 4, 2021 | Jan 2, 2022 |
| 2022 | 52 | Jan 3, 2022 | Jan 1, 2023 |
| 2023 | 52 | Jan 2, 2023 | Dec 31, 2023 |
| 2024 | 52 | Jan 1, 2024 | Dec 29, 2024 |
| 2025 | 52 | Dec 30, 2024 | Dec 28, 2025 |
| 2026 | 53 | Dec 29, 2025 | Jan 3, 2027 |
| 2027 | 52 | Jan 4, 2027 | Jan 2, 2028 |
| 2028 | 52 | Jan 3, 2028 | Dec 31, 2028 |
| 2029 | 52 | Jan 1, 2029 | Dec 30, 2029 |
| 2030 | 52 | Dec 31, 2029 | Dec 29, 2030 |