Day of the week calculator
Enter a Gregorian date to see which weekday it falls on, whether it is a birthday, an upcoming appointment or a historical event.
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Processing and privacy: The result is calculated inside your browser and your data is not sent to any server.
How to use it
- Enter date.
- The result appears straight away and updates as you edit.
- Copy the result, or copy a link that keeps the same values to share it.
How it is calculated
We count the days between the date and 1970-01-01 (a Thursday), then take the remainder after dividing by 7 to get the weekday. Occurrence in the month = day of month ÷ 7, rounded up.
Example
Inputs: Date = 2000-01-01. Result: Weekday: Saturday; Day of the year: 1; Occurrence in the month: 1st Saturday of January.
Limits and caveats
- Dates before 15 October 1582 use the proleptic Gregorian calendar, so they can differ from the Julian calendar dates written in sources of that time.
Questions about this tool
How do I find the day I was born?
Enter your full date of birth and the calculator shows the weekday straight away.
Why is 1 January 2000 in week 52 of 1999?
ISO 8601 starts week 1 with the week that holds the first Thursday of January. 1 January 2000 was a Saturday, so it belongs to the last week of 1999.
What does occurrence in the month mean?
It is which time that weekday appears in the month, so 30 September 2026 is the 5th Wednesday of September.