Day of the Week Calculator
Find which weekday a specific date falls on, including its day of year and ISO week.
✓ Free calculator ✓ Clear inputs ✓ Works in your browser
Day of the Week Finder
Discover the weekday and calendar details for any date.
Start Your Calculation
Free, instant and processed in your browser
Calculation Result
CalculatedHow to use the Day of the Week Calculator
- Select a valid calendar date.
- Click Calculate or choose Use Today.
- Read the weekday, day number within the year, and ISO week number.
How does this calculator work?
The date is interpreted in the Gregorian calendar. The weekday is computed from the UTC day of the selected date, so local daylight saving does not change the answer. Day of year starts at 1 on January 1. The ISO week shown may belong to the previous or following ISO week-year near New Year.
Calculation example
January 1, 2000 was a Saturday. January 1, 2021 was a Friday and belongs to ISO week 53 of 2020.
Frequently asked questions
Can I check a historical date?
Yes, within the supported Gregorian range from 1600 to 9999. Very old historical dates may have used other local calendars.
Is a date’s weekday affected by my time zone?
No. The selected date is a calendar date, not an instant on a clock.
Does the tool tell me whether it is a weekend?
Yes. Saturday and Sunday are labeled as weekends.
Why can ISO week-year differ from the calendar year?
ISO week 1 is the week containing January 4, so dates near New Year can be in a neighboring ISO week-year.
Is the tool free?
Yes. No account is required to check a date.