Day of the Week Calculator

Find what day of the week any date falls on — past, present, or future.

Calculator Numbers & Math Updated Apr 20, 2026
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How to Use
  1. Pick a date.
  2. Day of week + day of year + ISO week are shown.
Input
Result

Notes

ISO week
week 1 = first week with a Thursday in it (Monday-start)
Day of year
1 = Jan 1, up to 365 or 366 in leap years

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