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Day of the Week Calculator
Enter any year, month, and day to instantly find out which day of the week it falls on.
How This Calculator Works
This tool uses Zeller’s congruence, a well-known algorithm for computing the day of the week for any Gregorian calendar date, past or future, without needing a calendar lookup table.
The Method
Zeller’s congruence treats January and February as months 13 and 14 of the previous year, then combines the day, adjusted month, and century/year-within-century terms with a specific weighted formula to produce a remainder from 0-6, which maps directly to a day name.
- This calculator assumes the Gregorian calendar, which is the standard calendar used internationally today.
- Dates before the Gregorian calendar’s adoption (mid-1582 in most of Europe, later elsewhere) may not match historical records exactly.
- Provided for general reference and planning purposes.
Last reviewed August 2026