Day of the Week Calculator
Find out exactly what day of the week any date falls on.
Enter a Date
What is the Day of the Week Calculator?
The Day of the Week Calculator is a historical calendar tool that determines the exact weekday (Monday, Tuesday, etc.) of any historical or future date. It is heavily used by genealogists, historians, and event planners.
How It Works (Formula)
The calculator uses Zeller's Congruence, a famous mathematical algorithm developed by Christian Zeller. It calculates the day of the week based on the day of the month, the specific month code, the year of the century, and the zero-indexed century itself.
$$ h = \left( q + \lfloor\frac{13(m+1)}{5}\rfloor + K + \lfloor\frac{K}{4}\rfloor + \lfloor\frac{J}{4}\rfloor - 2J \right) \pmod 7 $$
Zeller's Congruence for the Gregorian calendar.
How to Use It
Simply enter any date in history (or any future date) into the input fields. Click calculate, and the tool will bypass calendar anomalies and leap years to output the precise day of the week that date occurred on.