Day of Week Calculator
Find out what day of the week any date falls on using Zeller's formula.
What Is the Day of Week Calculator?
Given any date in history or the future, you can calculate which day of the week it falls on using algorithms like Zeller's congruence or the Doomsday algorithm.
Formula
How to Use
Enter any date using the date picker. The calculator instantly shows the day of the week and additional calendar information like week number and day of year.
Example Calculation
January 1, 2000 was a Saturday. December 25, 2024 falls on a Wednesday. The calculator verifies historical dates like what day the moon landing was (July 20, 1969 — Sunday).
Understanding Day of Week
Day of Week Calculator is a free online tool that helps you solve real-world problems instantly. Whether you are a student, professional, or curious learner, this calculator provides accurate results with clear explanations.
Our tool uses proven mathematical formulas and algorithms to deliver precise calculations. All computations happen in your browser — no data is sent to any server.
Bookmark this page for quick access whenever you need to perform day of week calculator calculations.
Frequently Asked Questions
How accurate is it for ancient dates?
The calculator uses the Gregorian calendar. For dates before October 15, 1582, results reflect the proleptic Gregorian calendar, not the Julian calendar in use at the time.
What is the week number?
ISO week numbering starts on Monday. Week 1 is the week containing the year"s first Thursday.
Is the year 2100 a leap year?
No! Century years (1800, 1900, 2100) are not leap years unless divisible by 400. So 2000 was a leap year but 2100 will not be.
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