Week 40 2026: September 28–4, 2026
Week 40 starts on Monday, September 28, 2026 and ends on Sunday, October 4, 2026.
Quick answer
Week 40 of 2026 is the seven-day ISO week from September 28, 2026 to October 4, 2026. ISO weeks always run from Monday to Sunday.
Use week 40 in professional planning
This permanent week reference can be used in project plans, payroll notes, weekly reports, production schedules and deadline documents. Share the week number together with the ISO year and exact date range to avoid ambiguity around New Year.
For calculations that span more than one week, use the weeks between dates calculator. For work schedules, compare the same range with the business days calculator or open the project timeline calculator.
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FAQ
What are the dates for week 40 of 2026?
The dates are September 28, 2026 through October 4, 2026.
What day does this week start?
It starts on Monday.
What day does this week end?
It ends on Sunday.
How should I write this week in a report?
Use “ISO week 40 of 2026 (Sep 28–Oct 4, 2026)” so the week-year and date range are both clear.