What Week: Week 40
Find the calendar dates covered by any ISO week number.
ISO Week 40 of 2026 runs from September 28 to October 4, 2026, spanning two calendar months, with roughly 12 ISO weeks remaining in the year after it. ISO 8601 weeks always run Monday through Sunday and belong to the year containing that week's Thursday, which is why the first few days of January sometimes belong to the final week of the previous year. the End of the Federal Fiscal Year falls within this week in 2026. Next year, 2027, the same week number runs from October 4 to October 10, 2027 instead, since the exact dates shift slightly every year.
As of October 1, 2026, 12:19 PM (America/New York).
Position in the Year
Week 40 falls in the second half of the year, roughly 77% of the way through 2026's 52-53 ISO weeks.
Quarter Overlap
This week sits in calendar Q3, based on its Monday (September 28).