Day of the Week

Find what day of the week a date falls on

Date

How It Works

Find the day of the week for any date using Zeller's congruence algorithm.

The day of the week calculator determines which day of the week any given date falls on. It uses Zeller's congruence, a mathematical algorithm developed by Christian Zeller in the 19th century. The algorithm works by converting the date into a numerical value and applying modular arithmetic.

In Zeller's congruence, January and February are treated as months 13 and 14 of the previous year, which simplifies the calculation. The result maps to a number 0 through 6, corresponding to Saturday through Friday in the traditional Zeller mapping.

The days of the week are named after celestial bodies and Norse gods: Sunday (Sun), Monday (Moon), Tuesday (Tyr), Wednesday (Odin), Thursday (Thor), Friday (Frigg), and Saturday (Saturn). The ISO standard defines Monday as the first day of the week.

Results

Enter values to see results

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Quick Tips

• Results update automatically as you type
• Use Tab to navigate between fields
• Press Enter to calculate

Frequently Asked Questions

How does the Day of the Week work?

Simply enter your values into the input fields above. The Day of the Week uses standard formulas to compute results instantly as you type or click.

Is the Day of the Week free?

Yes, this calculator is completely free to use. No registration, no hidden fees, no limits.

How accurate are the results?

Results are computed using industry-standard mathematical formulas. For critical decisions, we recommend consulting a professional.

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