Weekmark

Calendar week · ISO 8601

Week 40, 2026

Monday 28 September – Sunday 4 October 2026

  1. Mon28Sep
  2. Tue29Sep
  3. Wed30Sep
  4. Thu1Oct
  5. Fri2Oct
  6. Sat3Oct
  7. Sun4Oct
ISO week
2026-W40
Copy as
CW40 (28 Sep – 4 Oct)
Quarter
Q4 2026
Weeks in 2026
53
US week number
40

Week 40 is also written KW 40 (Kalenderwoche) or CW 40. 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 28 Sep to Saturday 3 Oct the same number: week 40.