Day of the Week Calculator
Find what day of the week any date falls on — past or future. Plus the day of the year, week number, and quarter.
Inputs
Day of the week
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Day of year
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ISO week number
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Calendar quarter
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ISO 8601 format
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About Day of the Week Calculator
How week numbers work
This uses ISO 8601: weeks start on Monday, and week 1 is the week containing the year’s first Thursday. So January 1 might fall in week 52 or 53 of the previous year.
Day of year
January 1 is day 1, December 31 is day 365 (or 366 in leap years). Useful for project tracking, finance day-counts, and astronomy.
Range
JavaScript Date handles dates from around 271,000 BCE to 275,000 CE in theory — but accuracy declines at extremes. For dates near today, results are exact.