What day of the week is any date?
Pick a date and see the exact weekday it falls on, plus its day of the year, ISO week number, whether the year is a leap year, and how far it sits from today.
Your date
The weekday is computed with the JavaScript Date engine and cross-checked with Zeller's congruence, so every calendar quirk is handled automatically.
What this date tells you
The date at a glance
The same date, year by year
The weekday drifts forward one day most years and two days across a leap year, so the pattern repeats on a 28-year cycle (and exactly every 400 years in the Gregorian calendar).
| Year | Full date | Weekday | Day of year | Week | Leap |
|---|
Checking it by hand with Zeller's congruence
Calendars, weekdays and week numbers
How to Determine the Day of the Week
The day of the week for any date can be determined using mathematical algorithms like Zeller's congruence or the Doomsday algorithm. This calculator uses the built-in JavaScript Date engine, which handles all calendar quirks automatically.
Week Numbers Explained
The ISO week number system numbers weeks from 1 to 52 or 53, starting on Monday. Week 1 is the week containing the first Thursday of the year. This system is widely used in business, manufacturing, and international scheduling.
Day of the Year
The day number tells you where a date falls within the year, from 1 (January 1) to 365 or 366 (December 31). This is useful for agriculture, astronomy, and logistics where ordinal dates are standard.
Historical and Future Dates
This calculator works for both historical and future dates. Find out what day of the week you were born, when a holiday will fall next year, or what day a historical event occurred on.
Common questions
What day of the week was I born?
Enter your birth date in the calculator to find out. The result will show the exact day name (Monday, Tuesday, etc.) along with additional information about that date.
How is the week number calculated?
The calculator uses the ISO 8601 week numbering system. Weeks start on Monday, and the first week of the year is the one containing the first Thursday of January.
Does this work for dates before 1900?
Yes. The calculator handles dates across a very wide range. However, keep in mind that the Gregorian calendar was adopted at different times in different countries, so very old dates may not match historical records in some regions.
Why does January 1 sometimes fall in week 52 or 53?
In the ISO system, if January 1 falls on a Friday, Saturday, or Sunday, it belongs to the last week of the previous year. Week 1 of the new year starts on the following Monday.
The Gregorian calendar is used throughout. Very old dates may not match historical records in regions that adopted the Gregorian reform later than others.