ISO week 2026-W21

Week 21, 2026

Monday, May 18 – Sunday, May 24, 2026

ISO week 21 of 2026 (2026-W21) runs from Monday, May 18, 2026 to Sunday, May 24, 2026.

This week ended 21 weeks ago. The current week is week 42, 2026.

The 7 days of week 21

Dates in week 21, 2026
Day	Date	Day of year	US week	ISO date
Monday	May 18, 2026	138 of 365	21	2026-W21-1
Tuesday	May 19, 2026	139 of 365	21	2026-W21-2
Wednesday	May 20, 2026	140 of 365	21	2026-W21-3
Thursday	May 21, 2026	141 of 365	21	2026-W21-4
Friday	May 22, 2026	142 of 365	21	2026-W21-5
Saturday	May 23, 2026	143 of 365	21	2026-W21-6
Sunday	May 24, 2026	144 of 365	22	2026-W21-7

Week 21 at a glance

ISO code: 2026-W21 (Monday is 2026-W21-1, Sunday is 2026-W21-7)
Month: May
Quarter: Q2 of 2026
Day of year: Days 138–144 of 365
US week number: Monday–Saturday: US week 21; Sunday: US week 22 (Sunday-start weeks, week 1 contains January 1)
Even or odd: Week 21 is an odd week
Weeks left: After this week, 32 ISO weeks remain in 2026 (53 weeks in total)
Year progress: By Sunday, 39% of 2026 has passed

Holidays and key dates

There are no US federal holidays, daylight saving time changes or quarter starts in week 21 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 21, 2026

What are the dates of week 21 in 2026?

Week 21 of 2026 starts on Monday, May 18, 2026 and ends on Sunday, May 24, 2026.

What month is week 21 of 2026?

Week 21 falls in May. By the Thursday rule that ISO 8601 uses for years and quarters, it counts as a May week.

How do I get week 21 of 2026 in Excel or Google Sheets?

=ISOWEEKNUM(DATE(2026,5,18)) returns 21. To go the other way, =DATE(2026,1,4)-WEEKDAY(DATE(2026,1,4),2)+1+(21-1)*7 returns the Monday, May 18, 2026.