Day of the Week Calculator - Birthday Day Finder
Find the day of the week (Monday-Sunday) for any calendar date. Calculates leap years and day counts step-by-step using Zeller
Inputs Configuration
Calculation Output Status
Successfully Solved
Solved
DAY NAMESunday
IS LEAP YEARfalse
DAY OF YEAR186
TOTAL DAYS IN YEAR365
Step-by-Step Derivation Logs
1. Applying Zeller's Congruence for Gregorian calendar date: 2026-07-05
2. Century parameters derived: year of century (K) = 26, zero-based century (J) = 20.
3. Formula components:
4. - Day component (q) = 5
5. - Month factor ⌊13(m+1)/5⌋ = ⌊13(7+1)/5⌋ = 20
6. - Year factor K = 26
7. - Exponent factor ⌊K/4⌋ = 6
8. - Century factor ⌊J/4⌋ = 5
9. - Century subtractor -2J = -40
10. Raw equation sum = 22. Modulo index = (22 % 7) normalized = 1.
11. Index 1 corresponds to: Sunday.