How-to · Day of the Week
How to Determine the Exact Calendar Day of the Week You Were Born On
Quick answer
To determine the exact day of the week for any birthdate manually, apply Zeller’s
Step by step
- Apply zeller’s
Zeller's Congruence Calculation Formula
Zeller's Congruence uses an exact mathematical formula to map any date to its correct weekday. Note that in this system, January and February are counted as months 13 and 14 of the *previous year* to keep the leap year math accurate. Zeller's Formula: h = (q + ⌊(13(m+1))/5⌋ + K + ⌊K/4⌋ + ⌊J/4⌋ - 2J) mod 7 Where: q = Day of the month; m = Month index; K = Year of the century; J = Zero-based century index.
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