How can I find what day of the week a date was?
Enter the date and the calculator returns its weekday using the Gregorian calendar, along with the day number of the year and ISO week number.
Calendar lookup
Day of the week calculator
Enter any date to see its weekday and useful calendar-position details instantly.
Day of the week
Result
Details
- Accuracy note
The weekday follows the proleptic Gregorian calendar used by modern browsers. Very old historical dates may have used a different local calendar at the time.
How to find the weekday of a date
- Enter any valid Gregorian calendar date.
- Read the weekday immediately.
- Use the additional day-of-year and ISO week-number results when needed.
Weekday lookup uses
- Check birthdays, anniversaries, deadlines and historical dates.
- Find the ISO week and position of a date within the year.
Common questions
What is an ISO week number?
ISO weeks begin on Monday. Week 1 is the week containing the year’s first Thursday, so the final days of December can belong to week 1 of the next ISO week-year.
Are very old historical dates always represented correctly?
The browser uses a proleptic Gregorian calendar. A historical location may have used a different civil calendar at that time, so very old dates need local historical context.