Day of the Week Calculator
Find the day of the week for any date in the past or future, such as the day you were born.
What day was it?
Enter any date to see which day of the week it fell on, or will fall on, along with the same date over the next five years. It is useful for birthdays, anniversaries, historical events and planning.
June 15, 1990 was a Friday.
How it is worked out
The Gregorian calendar repeats exactly every 400 years. Within that cycle, each ordinary year shifts a fixed date forward by one weekday and each leap year by two. Algorithms such as Zeller's congruence turn that rule into a formula; this calculator counts days directly, which gives the same answer.
Fun facts
- Your birthday moves forward one weekday each year, or two after February 29.
- A calendar can be reused exactly every 6, 11 or 28 years for ordinary years.
- The Gregorian calendar began in 1582; earlier dates in many countries used the Julian calendar, so historical weekdays may differ from local records.
Frequently asked questions
What day of the week was I born?
Enter your birth date above to find out.
Why does my birthday change weekday each year?
A 365-day year is 52 weeks plus one day, so each date moves forward one weekday, or two after a leap day.
Does this work for dates before 1900?
Yes, using the Gregorian calendar, which may differ from Julian dates used historically in some countries.
Last reviewed October 2026. Results are estimates; check important decisions with a qualified professional.