Birth Day Calculator - Find Day of the Week
Calculate your birth day of the week, exact age in years and days, total days lived, zodiac sign, and Chinese zodiac. Useful for birthday facts, astrology, numerology, and historical date verification. Supports any date from 1900 to 2100.
Zeller's Algorithm
h = (q + ⌊13(m+1)/5⌋ + K + ⌊K/4⌋ + ⌊J/4⌋ - 2J) mod 7Variables:
- hDay (0=Saturday, 1=Sunday, ...)Day (0=Saturday, 1=Sunday, ...)(e.g.: 3 = Tuesday)
- qDay of monthDay of month(e.g.: 15)
- mMonth (Mar=3, Apr=4, ..., Jan=13, Feb=14)Month (Mar=3, Apr=4, ..., Jan=13, Feb=14)(e.g.: 7 = July)
- KYear mod 100Year mod 100(e.g.: 98 (from 1998))
- JYear ÷ 100Year ÷ 100(e.g.: 19 (from 1998))
How to Use
- 1
Enter Birth Date
Input day, month, and year of birth.
- 2
Click Calculate
The system calculates the weekday using a calendar algorithm.
- 3
View Results
Birth weekday, zodiac, and interesting facts are displayed.
Examples
Finding Birth Weekday
Problem:
What weekday was August 17, 1945?
Solution:
- 1.Using Zeller's algorithm or calendar lookup
- 2.Year 1945, August, day 17
Result:Friday
Indonesia's independence proclamation was read on a Friday.
Modern Birth Date
Problem:
What weekday was January 1, 2000?
Solution:
- 1.The new millennium began at Y2K
- 2.Using the Gregorian calendar
Result:Saturday
The year 2000 began on a Saturday.
Frequently Asked Questions
Is it accurate for old dates?
For dates after October 15, 1582 (Gregorian calendar adoption), it is 100% accurate. Earlier dates require conversion from the Julian calendar with different rules.
Is there meaning or folklore about birth weekdays?
An old rhyme says: "Monday's child is fair of face, Tuesday's child is full of grace..." In Javanese tradition, Weton combines weekday with market day (Legi, Pahing, Pon, Wage, Kliwon).
How do you find Weton?
Weton combines weekday (Monday–Sunday) with Javanese market day (5-day cycle: Legi, Pahing, Pon, Wage, Kliwon). The cycle repeats every 35 days (5×7).
Why is Zeller's algorithm complex?
The Gregorian calendar has complex rules (leap years every 4 years except century years except every 400 years). Zeller's formula encapsulates all these rules in one equation.