Day of Week Calculator

Find what day of the week any date falls on, including birthday weekdays, ISO day numbers, day of year, week number, weekend status, and leap-year details.

100% Browser-Based•Local Processing

Weekday Finder

Find the weekday for any date

Pick a date with the custom calendar and get the weekday, ISO day number, day of year, ISO week, weekend status, and nearby matching weekdays.

Weekday Result

Selected weekdayReadyChoose a date to find its weekday.
ISO day number--
Day of year--
ISO week--
Status--
Leap year--
Quarter--
No weekday result yet.
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Privacy Focused

🔒 Local Processing. Your data never leaves your device.

Instant Results

🌐 Fully Client-Side. Runs instantly in your browser.

No Signup

⚡ No accounts. No hassle. Just open and use.

Browser Based

🚀 Works right in your browser. No installs, no downloads.

Overview

Find the Weekday for Any Date

A day of week calculator answers questions such as what day was I born, what weekday is this deadline, what day was a historical date, or what weekday will a future event fall on. This page gives the weekday name and supporting calendar facts in one compact result panel.

Direct answer: Enter any Gregorian calendar date to find the weekday name, ISO day number, day of year, ISO week number, weekend or weekday status, leap-year status, quarter, and nearby dates that fall on the same weekday.

Use it for birthdays, anniversaries, payroll schedules, school timetables, historical research, genealogy, event planning, and spreadsheet checks. If you need the number of days between two dates after finding the weekday, use the Date Difference Calculator.

Day of Week Calculator with custom calendar picker, weekday wheel, ISO week result, day of year result, and nearby matching weekday dates
The Day of Week Calculator turns one selected date into weekday name, ISO week details, day-of-year facts, weekend status, and nearby matching weekdays.
Features

Weekday Finder Features Built for Real Calendar Questions

Custom calendar pickerChoose a date from a themed calendar overlay instead of relying on a default browser picker.
Weekday wheelA visual seven-day cycle highlights the selected weekday for quick recognition.
ISO detailsSee ISO day number and ISO week number for software, reporting, and planning workflows.
Day-of-year factsFind whether the date is day 1 through 365 or 366 in leap years.
Weekend statusQuickly see whether the selected date is a weekday or weekend.
Nearby matchesFind previous and next dates that land on the same weekday.
Use Cases

Day of Week Searches Covered by This Tool

This page covers the common ways users search for weekday lookup help, from birthdays to future events and ISO week checks.

Day of week calculatorFind the weekday name for any selected date using a direct browser calculation.
What day of the week was I bornChoose a birthday to see whether you were born on Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, or Sunday.
Weekday calculatorUse the custom calendar to check past, present, or future weekdays without opening a full calendar.
Find day of week for any dateEnter a date manually in YYYY-MM-DD format or select it from the custom picker.
What day was this dateUse historic presets or type the date to check events, records, genealogy notes, and archives.
Birthday weekday calculatorThe birthday preset shows how the tool handles birth dates and weekday names.
Day of year calculatorThe facts panel shows the ordinal day of the year, which is useful for logs, schedules, and countdowns.
ISO week number calculatorThe result includes ISO week number and ISO day number for business and software planning.
Comparison

Why Use a Weekday Calculator Instead of Checking a Calendar Manually?

A calendar works for nearby dates. A calculator is faster for old dates, future dates, ISO week details, and copyable summaries.

TaskRandomly.onlineManual method
Birthday weekdayReturns the exact weekday and a copyable summary.Requires scrolling through a calendar year.
Historical dateWorks instantly for old dates in the Gregorian calendar.Physical calendars are hard to find for past centuries.
ISO week detailsShows ISO day number and ISO week number together.Manual calendars usually hide ISO details.
Weekend checkLabels the date as weekday or weekend.Requires interpreting the weekday yourself.
Guide

How to Use Day of Week Calculator

Pick one date and let the calculator explain its weekday and calendar facts.

Choose a preset or date

Use Today, Birthday example, Historic date, Future date, or open the custom calendar picker to choose any date.

Read the weekday result

The main result shows the weekday name and the selected date in a readable format.

Check ISO and day-of-year facts

Review ISO day number, day of year, ISO week number, weekend status, leap-year status, and quarter.

Use nearby matching weekdays

The nearby list shows previous and next dates that fall on the same weekday.

Copy the summary

Copy the weekday result into a message, school note, planning document, spreadsheet, or research note.

Support

Frequently Asked Questions

How do I find what day of the week a date was?

Enter the date or choose it from the custom calendar picker. The calculator shows the weekday name, ISO day number, day of year, ISO week number, weekend status, and related calendar facts.

What day of the week was I born?

Enter your birth date and the main result will show the weekday you were born on. The birthday preset gives a quick example of this workflow.

Can this find the weekday for a future date?

Yes. Enter any future Gregorian calendar date or use the Future date preset. The result works the same way for future dates, current dates, and past dates.

Does this work for historical dates?

Yes for Gregorian calendar dates. Very old records may use different historical calendar systems depending on country and period, so check the calendar system if you are doing formal research.

What is ISO day number?

ISO day number uses Monday as 1 and Sunday as 7. It is common in software, reporting, payroll, and ISO-8601 date workflows.

What is day of year?

Day of year is the date ordinal from 1 to 365, or 1 to 366 in a leap year. For example, January 1 is day 1.

Does the calculator show ISO week number?

Yes. The result includes ISO week number, which is useful for work schedules, reporting periods, planning dashboards, and calendar systems.

Can I check whether a date is a weekend?

Yes. The status card labels the date as a weekend or weekday based on the calculated weekday.

Does the calculator account for leap years?

Yes. Leap years affect day-of-year values and some week calculations. The facts panel shows whether the selected year is a leap year.

What formula is used to find the day of week?

Browsers can compute weekdays from Gregorian dates directly. Many manual methods use algorithms such as Zeller congruence or the Doomsday rule to reach the same weekday result.

Is my selected date stored online?

No. The weekday calculation runs locally in your browser and does not upload your selected date or copied summary.

What is the difference between this and a date difference calculator?

A day of week calculator tells you which weekday a single date falls on. A date difference calculator measures the duration between two dates.

Still have questions?

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