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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.
公式
weekday = (Zeller's congruence or similar algorithm)
- date
- Date (YYYY-MM-DD) — Input date
- weekday
- Day of week (text) — Monday, Tuesday, ..., Sunday
ステップバイステップガイド
- 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
解いた例
入力
January 1, 2000
結果
Saturday
入力
July 4, 1776
結果
Thursday
入力
December 25, 2026
結果
Friday
よくある質問
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.
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