Week Numbers 2021
How many ISO weeks are in 2021?
Answer
2021 ended on Friday, December 31, 2021. Its last ISO week, week 52, ran until Sunday, January 2, 2022.
January 1, 2021, is a Friday, a common year → 52 ISO weeks (53 only when January 1 is a Thursday, or a Wednesday in a leap year)
Next
All 52 ISO weeks of 2021
| Week | Monday | Sunday |
|---|---|---|
| 1 | ||
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| 51 | ||
| 52 |
ISO weeks are always whole, Monday to Sunday, so the numbering of 2021 starts on Monday, January 4, 2021, and ends on Sunday, January 2, 2022.
Other ways to count the weeks of 2021
Counted as whole blocks of seven days inside the calendar year, 2021 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) 2021 has 52 weeks, and week 1 starts on Sunday, December 27, 2020.
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
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 |
FAQ
How many ISO weeks are in 2021?
When does week 1 of 2021 start?
When does the last week of 2021 end?
Why does 2021 have 52 ISO weeks?
See Also
- Week Numbers 2020: All 53 ISO Weeks with Dates
- Week Numbers 2022: All 52 ISO Weeks with Dates
- Week Numbers 2023: All 52 ISO Weeks with Dates
- Week Numbers 2024: All 52 ISO Weeks with Dates
- Week Numbers 2025: All 52 ISO Weeks with Dates
- Week Numbers 2026: All 53 ISO Weeks with Dates
- Week Numbers 2027: All 52 ISO Weeks with Dates
- Week Numbers 2028: All 52 ISO Weeks with Dates
- Week Numbers 2029: All 52 ISO Weeks with Dates
- Week Numbers 2030: All 52 ISO Weeks with Dates
- Номера недель 2021 года: все 52 недели с датами
- Semanas del año 2021: las 52 semanas con fechas
- Semanas do ano 2021: as 52 semanas com datas