July 20, 1969 was a Sunday. December 25, 2030 falls on a Wednesday. Enter any date and this calculator tells you the weekday, day-of-year number and week number. Works for past and future dates.
Day of Week Calculator - What Day Was Any Date?
July 20, 1969 was a Sunday. December 25, 2030 falls on a Wednesday. Enter any date and this calculator tells you the weekday, day-of-year number and week number. Works for past and future dates.
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Every date maps to exactly one weekday
| Date | Day | What happened |
|---|---|---|
| July 20, 1969 | Sunday | Apollo 11 Moon landing |
| November 9, 1989 | Thursday | Fall of the Berlin Wall |
| January 1, 2000 | Saturday | Y2K - the millennium bug did not bite |
| February 29, 2024 | Thursday | Most recent leap day |
| December 25, 2030 | Wednesday | Christmas - midweek that year |
Type any date and the calculator returns the weekday, day-of-year number (1 to 366) and ISO week number. Works backwards to historical dates and forward as far as you need.
How to find the day - step by step
- Enter a date - type in YYYY-MM-DD format (e.g. 2000-01-15) or DD.MM.YYYY (e.g. 15.01.2000). Both work.
- Read the result - the weekday name appears in a large display, along with the day-of-year number and the ISO week number. Weekend dates get a green badge, weekdays a blue one.
Use cases people actually search for
Enter your birthday - most people have never checked. Born on March 14, 1995? That was a Tuesday.
Is September 20, 2025 a Saturday? Check before booking the venue. (It is a Saturday.)
Will Christmas 2026 fall on a weekend? December 25, 2026 is a Friday - long weekend ahead.
D-Day (June 6, 1944) was a Tuesday. The attack deliberately targeted a weekday.
Accepted date formats
| Format | Example | Common in |
|---|---|---|
| YYYY-MM-DD | 2000-01-15 | ISO standard, databases, East Asia |
| DD.MM.YYYY | 15.01.2000 | Europe, most of the world |
| DD-MM-YYYY | 15-01-2000 | Alternative European notation |
Days that repeat - the calendar cycle
The Gregorian calendar repeats every 400 years exactly. Within that cycle, a given date shifts its weekday by 1 day per normal year and 2 days per leap year. That is why your birthday falls on a different day each year but eventually comes back around.
| Year | January 1 | Leap? | Shift from previous year |
|---|---|---|---|
| 2024 | Monday | Yes | +2 from Sunday (2023) |
| 2025 | Wednesday | No | +1 from Tuesday... wait, +2 because 2024 was leap |
| 2026 | Thursday | No | +1 from Wednesday |
| 2027 | Friday | No | +1 from Thursday |
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