Day of the Week Calculator
What day of the week was — or will be — any date? Find the weekday of a birthday, a holiday or a historical date.
Dates use your device’s calendar (Gregorian, also for dates before 1582).
Find the day of the week
Pick a date and the calculator shows its weekday, the day of the year and the ISO week number. It also lists the weekday of the same date in the years around it — handy for birthdays and anniversaries.
Examples: 1 January 2000 was a Saturday, the Moon landing on 20 July 1969 was on a Sunday, and Christmas Day 2026 is a Friday.
Why a date moves one weekday each year
A common year has 365 days, which is 52 weeks and 1 day. So the same date falls one weekday later the next year — or two weekdays later when a 29 February lies in between.
Dates before 1582
The calculator uses the Gregorian calendar for every date. Many countries used the Julian calendar before 1582 (and some until the 20th century), so historical sources can show a different date for the same day.
Frequently asked questions
What day of the week was I born?
Enter your date of birth: the calculator shows the weekday right away.
What day of the week is Christmas this year?
Choose the Christmas quick pick. In 2026, 25 December is a Friday.
How do I find the week number of a date?
The calculator shows the ISO week number, in which weeks start on Monday and week 1 contains the first Thursday of the year.