Day of the Week Calculator
Finds the day of the week for any date.
Day of the week
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Share sends a link that reopens these numbers. Copy details pastes the full breakdown as a list.
Date —
In its month —
ISO day number, Monday = 1 —
Type of day —
The formula
day of the week = (days since a known date) mod 7
1 January 1970 was a Thursday. Every seventh day after or before it is another Thursday.
What to watch out for
Dates before 1582, when the Gregorian calendar began, or before a country adopted it, are worked out as though it had always been in use, so they may not match the calendar used at the time.
Frequently Asked Questions
What day of the week was 1 January 2000?
A Saturday.
Why does a date move on by one weekday each year?
A common year is 52 weeks and 1 day, and a leap year is 52 weeks and 2 days. 1 March was a Friday in 2024 and a Saturday in 2025.