What is the Day of the Week Calculator?
Find what day of the week any date falls on, past or future. Dates are deceptively tricky — months have different lengths and leap years shift everything. These date and time calculators handle calendar math exactly, using UTC to avoid daylight-saving surprises.
How to use the Day of the Week Calculator
- Enter your date.
- Results update automatically as you type; you can also press Calculate.
- Read the output: day of the week, full date, day of the year, iso week number.
- Use the 📊 chart to see the result visually, then copy or share it.
Formula and method
Worked example
With date = 1969-07-20, the Day of the Week Calculator returns day of the week: Sunday; full date: Sunday, July 20, 1969; day of the year: 201.
Tips for better results
- Decide whether you need to include the end date when counting days.
- Business-day counts exclude weekends but not public holidays unless you subtract them.
- Timestamps are shown in UTC; convert to your local time zone as needed.
Frequently asked questions
What does the Day of the Week Calculator do?
Find what day of the week any date falls on, past or future.
How is it calculated?
The Day of the Week Calculator uses this method: Gregorian calendar computation (UTC).
Can you show an example?
With date = 1969-07-20, the Day of the Week Calculator returns day of the week: Sunday; full date: Sunday, July 20, 1969; day of the year: 201.
Is the Day of the Week Calculator accurate?
Yes. It uses standard formulas and exact constants, and the results are verified by our automated test suite. Values are displayed to up to 12 significant digits.
Is this tool free and private?
Yes — the Day of the Week Calculator is completely free with no sign-up, and it runs entirely in your browser, so the values you enter are never uploaded to our servers.
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