Week 21, 2026

1. Mon18May
2. Tue19May
3. Wed20May
4. Thu21May
5. Fri22May
6. Sat23May
7. Sun24May

ISO week

2026-W21

Copy as

CW21 (18–24 May)

Quarter

Q2 2026

Weeks in 2026

53

US week number

21

Week 21 is also written KW 21 (Kalenderwoche) or CW 21. ISO weeks start on Monday, and week 1 is the week with the year’s first Thursday. US calendars start weeks on Sunday and count the week with 1 January as week 1, so they give Monday 18 May to Saturday 23 May the same number: week 21.