What Week: Week 12
Find the calendar dates covered by any ISO week number.
ISO Week 12 of 2026 runs from March 16 to March 22, 2026, with roughly 40 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. St. Patrick's Day, the First Day of Spring, Eid al-Fitr fall within this week in 2026. Next year, 2027, the same week number runs from March 22 to March 28, 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 12 falls in the first half of the year, roughly 23% of the way through 2026's 52-53 ISO weeks.
Quarter Overlap
This week sits in calendar Q1, based on its Monday (March 16).