What Week: Week 21
Find the calendar dates covered by any ISO week number.
ISO Week 21 of 2026 runs from May 18 to May 24, 2026, with roughly 31 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. No major U.S. holidays tracked by Dayswise fall within this specific week in 2026. Next year, 2027, the same week number runs from May 24 to May 30, 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 21 falls in the first half of the year, roughly 40% of the way through 2026's 52-53 ISO weeks.
Quarter Overlap
This week sits in calendar Q2, based on its Monday (May 18).