Week 51 in 2025
Week 51 of 2025 begins on December 15, 2025 and ends on December 21, 2025. It covers days 349 to 355 of the year and falls in quarter 4.
Weeks since this week: 43
Week 51 of 2025 at a glance
| Starts (Monday) | December 15, 2025 |
|---|---|
| Ends (Sunday) | December 21, 2025 |
| US week (Sunday to Saturday) | 51 (December 14, 2025) |
| Month | December |
| Quarter | Q4 |
| Days of the year | 349–355 |
| Year completed at the end of this week | 97.3% |
| Weeks left in 2025 after this week | 1 |
| Weeks in 2025 | 52 |
| Even or odd week | Odd |
Calendar for December 2025
Download Calendar in printable A4 PDF
(US version) (EU/ISO Version)
All Weeks in 2025:
Past & Future Week Number 51:
US and ISO week numbers
In the US system, where weeks start on Sunday and week 1 is the week that contains 1 January, this is week 51 of 2025. It runs from December 14, 2025 to December 20, 2025.
Even and odd weeks
Week 51 is an odd week. Even and odd week numbers are used for alternating schedules such as shift rotas, school timetables, custody arrangements and waste collection.
Week 51 in other years
| From | To | |
|---|---|---|
| Week 51 in 2023 | December 18, 2023 | December 24, 2023 |
| Week 51 in 2024 | December 16, 2024 | December 22, 2024 |
| Week 51 in 2026 | December 14, 2026 | December 20, 2026 |
| Week 51 in 2027 | December 20, 2027 | December 26, 2027 |
How week numbers are counted
Most of the world numbers weeks according to the ISO 8601 standard. A week starts on Monday, and week 1 is the week that contains the first Thursday of the year, which is always the week that contains 4 January.
Week 1 of 2025 began on December 30, 2024. 2025 has 52 ISO weeks.
Because of this rule, the first days of January can belong to the last week of the previous year, and the last days of December can belong to week 1 of the next year.
In the United States, weeks usually start on Sunday and week 1 is the week that contains 1 January, so the US week number can differ from the ISO week number.
Find the week number of a date
Frequently Asked Questions (FAQ)
When does week 51 of 2025 start and end?
Week 51 of 2025 starts on December 15, 2025 and ends on December 21, 2025 (ISO 8601, Monday to Sunday).
Which month is week 51 of 2025 in?
Week 51 of 2025 is in December.
What dates are in week 51 of 2025?
December 15, 2025, December 16, 2025, December 17, 2025, December 18, 2025, December 19, 2025, December 20, 2025, and December 21, 2025
How many weeks does 2025 have?
2025 has 52 ISO weeks.
Is week 51 an even or odd week?
Week 51 is an odd week.
What is the US week number for this week?
In the US system, where weeks start on Sunday and week 1 is the week that contains 1 January, this is week 51 of 2025. It runs from December 14, 2025 to December 20, 2025.