Day of the Week Calculator
Find what day of the week any date falls on.
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How it works
Pick any date — past or future — and the tool tells you which day of the week it falls on. It also shows the day number within the year, the ISO week number, and whether the year is a leap year. The calculation uses the browser's date engine, which follows the proleptic Gregorian calendar, so results are correct across centuries. Everything runs locally in your browser with no lookups.
date → weekday (Mon–Sun)
Common use cases
- Finding what day of the week you were born.
- Checking which weekday a future deadline falls on.
- Confirming the weekday of a historical date.
Frequently asked questions
Does it work for old historical dates?
It uses the proleptic Gregorian calendar (today's calendar projected backward), so weekdays are consistent across centuries. Note that some countries used the Julian calendar before adopting the Gregorian one, which can differ.
What extra information does it show?
Besides the weekday, it shows the day-of-year number, the ISO week number, and whether the year is a leap year.
Is anything sent to a server?
No. The weekday is computed locally by your browser.