Weekmark

Calendar week · ISO 8601

Week 51, 2026

Monday 14 December – Sunday 20 December 2026

  1. Mon14Dec
  2. Tue15Dec
  3. Wed16Dec
  4. Thu17Dec
  5. Fri18Dec
  6. Sat19Dec
  7. Sun20Dec
ISO week
2026-W51
Copy as
CW51 (14–20 Dec)
Quarter
Q4 2026
Weeks in 2026
53
US week number
51

Week 51 is also written KW 51 (Kalenderwoche) or CW 51. 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 14 Dec to Saturday 19 Dec the same number: week 51.