Find Weekday
Find out which weekday any given date falls on, so you can slot appointments and plans into the right weekly context. Runs in your browser, GDPR-compliant.
Your inputs are processed in your browser and are not transmitted to our servers. Note: third-party resources (e.g. advertising and analytics from Google/Cloudflare) and an optional PayPal donation link may transfer data when loading or when clicked. Browser extensions or plugins may be able to read content that is visible in the input fields.
The result will appear here …
How to use this tool (video)
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Find Weekday
The weekday calculator determines which day of the week any given date falls on. Whether it is a wedding anniversary, a milestone, or a historical event: this tool lets you instantly match any date to the correct weekday on the calendar. The computation happens directly in your browser, with no data sent to a server.
How it works
The calculator uses Zeller's congruence algorithm, a mathematical formula that determines the day of the week for any date in the Gregorian calendar. The formula accounts for day, month, and year, producing a value from 0 to 6 that corresponds to a weekday from Sunday through Saturday. As a concrete example, January 1, 2024 falls on a Monday. Plugging the date into the formula yields a remainder of 1, corresponding to Monday. Likewise, July 4, 1776, the day of the American Declaration of Independence, was a Thursday. The algorithm works for all dates from 1583 onward.
What the tool can and cannot do
This tool calculates the weekday for a single date in the Gregorian calendar. It cannot reform historical calendars, calculate leap years, or determine the span between two dates. It shows only the weekday, not the duration between data points. The calculator does not support pre-Gregorian dates, meaning it cannot handle dates before the introduction of the Gregorian calendar in 1582. For time spans or age calculations, a separate tool is required. It is not a substitute for a full calendar or scheduling software.
Why local processing in the browser
All calculations happen locally in your browser. Your inputs are never sent to a server, there is no upload and no server log files storing your data. You need no account and do not need to register. After the page loads, the calculator works offline too, because the assets are cached in the browser. There is no attackable server and nothing is transmitted over the network. You can freely enter dates and discard results, because nothing is stored or tracked. Local processing means the data does not need to be sent over a network, saving energy.
Frequently asked questions
How is the weekday calculated?
The calculator uses Zeller's congruence algorithm, a proven mathematical formula for Gregorian calendar computation.
Do I need to be online?
No, the calculator works offline after the page loads. The computation is purely local and requires no Internet connection.
Are my date inputs uploaded?
No, all inputs stay on your device. There is no upload, no server logs, and no third-party access to your data.
Does it work for all historical dates?
Yes, the algorithm works for all dates from October 15, 1582, when the Gregorian calendar was introduced.
Can I also find all dates on a specific weekday?
No, the calculator only returns the weekday for a given date. A reverse search for all dates on a specific weekday is not supported.
Is the calculator accurate?
Yes, Zeller's congruence algorithm produces an exact result for all valid Gregorian calendar dates.