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Week Number Calculator
Find the week number of any date instantly with our precision tech-noir suite.
Current Week21of 53 weeks in 2026
May 20, 2026Wednesday
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Convert Date to Week
ISO 8601
W21
US Week
21
Quarter
Q2
Day of Year
140
Remaining
225
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Convert Week to Dates
The week spans from:Monday May 18 — Sunday May 24, 2026
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Year 2026 Overview
Week #Monday — Sunday Range
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ISO 8601 Explained
The ISO 8601 week date system is an international standard for designating days and weeks. A year has 52 or 53 full weeks. Week 01 of any year is defined as the week with the first Thursday of the year in it.
- check_circleWeeks always start on a Monday.
- check_circleThe first week of the year is the one that contains January 4th.
- check_circleThe US system differs, often starting weeks on Sundays and defining Week 1 as the week containing January 1st.