How to Calculate Date to Day of Week
What is Date to Day of Week?
A date to day of week calculator determines which day of the week any calendar date falls on. Uses the Doomsday algorithm or JavaScript's built-in Date object for instant results.
Formula
weekday = (Zeller's congruence or similar algorithm)
- date
- Date (YYYY-MM-DD) — Input date
- weekday
- Day of week (text) — Monday, Tuesday, ..., Sunday
Step-by-Step Guide
- 1JavaScript Date parses the date string
- 2getDay() returns 0 (Sunday) through 6 (Saturday)
- 3The Gregorian calendar repeats every 400 years
- 4Any date in history or future can be calculated precisely
Worked Examples
Input
January 1, 2000
Result
Saturday
Input
July 4, 1776
Result
Thursday
Input
December 25, 2026
Result
Friday
Frequently Asked Questions
How can I tell what day a date falls on?
Use Zeller's congruence or a calendar algorithm. The calculator handles this automatically.
What if I need the ISO week number?
ISO weeks run Monday–Sunday, with week 1 containing January 4. Different from US Sunday-start weeks. Specify which standard is needed.
How far back does this work?
Gregorian calendar calculations are valid from Oct 15, 1582 onward. For earlier dates, consult historical sources.
Ready to calculate? Try the free Date to Day of Week Calculator
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