Week Number Calculator
Enter the required values or choose a complete example.
Conversion
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Find the ISO week-year, week and weekday for a calendar date, or convert an ISO week date to its Gregorian date.
Calendar date to ISO week
ISO week to calendar date
Calendar date to ISO week
ISO week to calendar date
Calendar date
(required)
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Choose a Gregorian calendar date. Typed/API dates use YYYY-MM-DD.
ISO week year
(required)
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Enter the ISO week year paired with the week number, which can differ from the calendar year.
ISO week number
(required)
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Enter an ISO week number that exists in the selected ISO week year.
ISO weekday
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Choose a weekday in the ISO Monday-to-Sunday order.
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday
Calculate
ISO conversion
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Interpretation
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Counting basis
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Calculation and counting rules
Calculation details
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