Time & Date
Enter any date to discover which day of the week it falls on, plus useful calendar details.
Day of the Week
Thursday
This is a weekday.
The calculator uses the ISO 8601 standard for week numbering (Monday as week start).
A day of the week calculator is a date-lookup tool that determines the weekday name for any date you enter. It also computes related calendar metrics: which number day within the year (1–366), the ISO 8601 week number (for business planning), whether the date is a weekend, and the count of days between that date and today. It handles leap years and all calendar complexities automatically.
The calculator takes a date input, uses the JavaScript Date API (or equivalent algorithms) to compute the weekday index (0=Sunday, 1=Monday, etc.), then looks up the day name. It simultaneously calculates the day-of-year by counting days from 1 January, the ISO week number using the ISO 8601 standard (which defines weeks as starting on Monday and week 1 as the first week with a Thursday), and the difference in days between the input date and today.
| Input | Result | Notes |
|---|---|---|
| Date: 22 July 2026 (today) | Wednesday, day 203 of year, ISO week 30, status: Today | Today's date is used as the default, giving you an instant reference for the current day and its calendar position. |
| Date: 25 December 2025 (Christmas) | Thursday, day 359 of year, ISO week 52, 151 days until today | Major holidays and past dates are easy to check; ISO week 52 indicates it's late in the year. |
| Date: 1 January 2020 | Wednesday, day 1 of year, ISO week 1, 2397 days since today | New Year 2020 was a Wednesday; day 1 confirms it is the first day of the year; ISO week 1 is standard for 1 January in most cases. |
ISO 8601 is an international standard for date and time notation. Week 1 is the first week with a Thursday (or equivalently, the week containing 4 January). Weeks start on Monday and end on Sunday. This system ensures consistency across countries and industries for business scheduling.
Day of the year (1–366) is used in scientific, environmental, and agricultural contexts to track seasonal progress, solar irradiance, or phenological cycles. It's also useful for time-series data and progress tracking within a single year.
Yes. The calculator works for any date in history and for future dates, as long as the date is valid in the proleptic Gregorian calendar (which extends the Gregorian calendar backwards to 1 January 1 AD).
The calculator uses the proleptic Gregorian calendar, which is mathematically consistent. However, historical dates before October 1582 (when the Gregorian calendar was adopted) may not align with actual weekdays in that era, as the Julian calendar was in use then.
A weekend is defined as Saturday or Sunday. This is the standard in most Western countries; some regions (e.g., Middle East) observe Friday–Saturday as the weekend, which this calculator does not account for.
The calculator accounts for leap years automatically. A year is a leap year if divisible by 4, except for years divisible by 100 (unless also divisible by 400). 2024 is a leap year; 1900 was not; 2000 was.