Day of the Week Calculator
Enter any date — past or future — to instantly find out what day of the week it falls (or fell) on.
Day of the week
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Enter a date to check.
How the Day of the Week formula works
This uses the standard Gregorian calendar's day-of-week calculation, which cycles through Monday–Sunday based on how many days have elapsed since a known reference date.
Step-by-step calculation
- Convert the entered date into a day count relative to a fixed reference date.
- Divide that day count by 7 and use the remainder to look up the corresponding day of the week.
Worked example
July 4, 1776 fell on a Thursday. December 25, 2030 will fall on a Wednesday.
Frequently asked questions
How far back or forward does this work accurately?
It's accurate for any date in the modern Gregorian calendar, which was adopted in most of the world starting in 1582 — dates before that, or in regions that adopted the Gregorian calendar later, may not align with this calculation.
Why do people look up the day of the week for their birthday?
It's a common bit of trivia — many people are curious which day of the week they were born on, since birth certificates typically only record the date, not the day name.