ISO week 2026-W51

Week 51, 2026

Monday, December 14 – Sunday, December 20, 2026

ISO week 51 of 2026 (2026-W51) runs from Monday, December 14, 2026 to Sunday, December 20, 2026.

This week starts 9 weeks from now. The current week is week 42, 2026.

The 7 days of week 51

Dates in week 51, 2026
Day	Date	Day of year	US week	ISO date
Monday	December 14, 2026	348 of 365	51	2026-W51-1
Tuesday	December 15, 2026	349 of 365	51	2026-W51-2
Wednesday	December 16, 2026	350 of 365	51	2026-W51-3
Thursday	December 17, 2026	351 of 365	51	2026-W51-4
Friday	December 18, 2026	352 of 365	51	2026-W51-5
Saturday	December 19, 2026	353 of 365	51	2026-W51-6
Sunday	December 20, 2026	354 of 365	52	2026-W51-7

Week 51 at a glance

ISO code: 2026-W51 (Monday is 2026-W51-1, Sunday is 2026-W51-7)
Month: December
Quarter: Q4 of 2026
Day of year: Days 348–354 of 365
US week number: Monday–Saturday: US week 51; Sunday: US week 52 (Sunday-start weeks, week 1 contains January 1)
Even or odd: Week 51 is an odd week
Weeks left: After this week, 2 ISO weeks remain in 2026 (53 weeks in total)
Year progress: By Sunday, 97% of 2026 has passed

Holidays and key dates

There are no US federal holidays, daylight saving time changes or quarter starts in week 51 of 2026.

Week numbers follow ISO 8601: weeks start on Monday and week 1 contains the first Thursday of the year. US weeks start on Sunday, with week 1 containing January 1.

Questions about week 51, 2026

What are the dates of week 51 in 2026?

Week 51 of 2026 starts on Monday, December 14, 2026 and ends on Sunday, December 20, 2026.

What month is week 51 of 2026?

Week 51 falls in December. By the Thursday rule that ISO 8601 uses for years and quarters, it counts as a December week.

How do I get week 51 of 2026 in Excel or Google Sheets?

=ISOWEEKNUM(DATE(2026,12,14)) returns 51. To go the other way, =DATE(2026,1,4)-WEEKDAY(DATE(2026,1,4),2)+1+(51-1)*7 returns the Monday, December 14, 2026.