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Weekday Calculator

Date & Time

Day of the week for any date

Quick Answer

Weekday Calculator: Day of the week for any date. Weekday Calculator uses standard date & time formulas to compute accurate results instantly.

2000-01-01

Saturday

Weekend 🎉 · day 1 of 366

Day of year1 / 366
Weekend?Yes
Nth Saturday of month1 / 5
Leap yearYes (366d)

Same month-day, nearby years

1997Wednesday1998Thursday1999Friday2001Monday2002Tuesday2003Wednesday2000Saturday

Verify with Kim Larsen formula

  1. 1Jan counts as month 13 of year 1999
  2. 2w = (d + 2m + ⌊3(m+1)/5⌋ + y + ⌊y/4⌋ − ⌊y/100⌋ + ⌊y/400⌋ + 1) mod 7
  3. 3Formula says Friday — matches calendar ✗
  4. 4Day-of-year: sum of months before + 1 = 1

💡 Weekdays repeat on a 28-year solar cycle (when leap years align), so a 1996 calendar works in 2024. Famous weekday trivia: the 2008 Beijing Olympics opened on 2008-08-08, a Friday; the PRC founding on 1949-10-01 was a Saturday. The Doomsday algorithm lets you compute any date mentally in seconds.

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How to Use

  1. Pick dates or a mode: select start/end dates or switch modes in the Weekday Calculator.
  2. Instant calculation: results appear immediately with day/week/month equivalents.
  3. Solve both ways: change any field and everything updates — forward or reverse.
  4. Check the context: read the solar-term/holiday/rule notes on this page.

Key Points

  • Weekday Calculator is a free online date & time tool — open and use, no sign-up.
  • All calculations run locally in your browser; your data never leaves the device.
  • Key capability: Day of the week for any date.
  • Results come with formulas and reference tables so you can verify every number.

Formula & How It Works

Weekday Calculator formula

Weekday Calculator uses standard date & time formulas to compute accurate results instantly.

FAQ

How do I use the Weekday Calculator?
Open the page and fill in the input fields — results update automatically. Day of the week for any date.
Are the results accurate?
Yes. Standard formulas and conversion factors are used and verified.
Is it free? Do I need to sign up?
Completely free. No registration, login or download required.
Does it work on mobile?
Yes. The responsive design works on phones, tablets and desktops.
Is my data saved?
No. Everything runs locally in your browser.

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Source & Updates

Based on standard calendar arithmetic. Last updated: 2025-07

Authoritative sources:

Last updated:

Formulas and content on this page are reviewed by the YiJianSuan team. For reference only — official sources prevail.

Maintained and periodically reviewed by the YiJianSuan editorial team — review process in ourEditorial Policy.

Cite this page: YiJianSuan. Weekday Calculator[EB/OL]. https://www.yijiansuan.com/en/c/date/weekday

Results provided by this tool are for reference only and do not constitute professional advice.