Week 51 of 2025 runs December 15, 2025 to December 21, 2025.
Week 51 starts on Monday, December 15, 2025 and ends on Sunday, December 21, 2025. It's the 349th day of the year, sits in Q4, and falls in December. By the end of this week, 355 of 365 days are gone, putting 2025 at 97.3%.
There are no public holidays this week, so all 5 weekdays are working days. Need a different week? Browse the full 2025 week calendar, or jump to this week's number.
Week 51 at a glance
The 7 days of week 51
Every date in week 51 of 2025, Monday through Sunday, with day-of-year numbers and events.
| Day | Date | Day no. | Type | Events |
|---|---|---|---|---|
| Monday | Day 349 | Weekday | ||
| Tuesday | Day 350 | Weekday | ||
| Wednesday | Day 351 | Weekday | ||
| Thursday | Day 352 | Weekday | ||
| Friday | Day 353 | Weekday | ||
| Saturday | Day 354 | Weekend | ||
| Sunday | Day 355 | Weekend | Winter Solstice |
What week 51 of 2025 means
ISO 8601 numbers weeks so every week starts on Monday and ends on Sunday. Week 1 is the one holding the year's first Thursday, which is why early January can land in week 52 or 53 of the previous year. Week 51 is one piece of that system.
In 2025, week 51 covers Dec 15 – Dec 21, 2025. That's December, deep in Q4. The same week number shifts by a day or two each year, so week 51 in 2026 won't share these exact dates. The table below shows how it moves.
Want to check a specific date instead of a week number? The week calculator converts any date to its ISO week. Curious how many weeks a year holds? The weeks in a year guide explains 52 versus 53. And the ISO week number page covers the standard end to end.
Holidays in week 51 of 2025
🇺🇸 United States
🇬🇧 United Kingdom
🇨🇦 Canada
🇦🇺 Australia
Week 51 across years
The same ISO week number lands on different dates each year. Here's how week 51 shifts.
| Year | From (Mon) | To (Sun) | Notable | |
|---|---|---|---|---|
| 2024 | view → | |||
| 2025 THIS YEAR | ||||
| 2026 | view → | |||
| 2027 | Christmas Day | view → | ||
| 2028 | view → |
Week 51 of 2025: questions and answers
What days are in week 51 of 2025?
Week 51 of 2025 runs from December 15, 2025 (Monday) through December 21, 2025 (Sunday). It spans December.
What month is week 51 in 2025?
Week 51 of 2025 falls entirely in December 2025.
How many working days are in week 51 of 2025?
Week 51 of 2025 has 5 working days.
What week is Winter Solstice in 2025?
Winter Solstice falls in ISO week 51 of 2025 (Dec 15 – Dec 21, 2025).
What quarter is week 51 of 2025 in?
Week 51 of 2025 is in Q4 (2025). The week starts on day 349 of 365.
What is ISO week 51?
ISO week 51 is defined by the ISO 8601 international standard. It begins on Monday, December 15, 2025, and ends on Sunday, December 21, 2025. It is week 98% through the ISO year 2025.