Day of the Week Calculator
Days of the Week
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About Day of the Week Calculations
The Doomsday Algorithm
Mathematicians have developed various methods to calculate the day of the week mentally. The most famous is the Doomsday Algorithm, created by John Conway. It uses anchor dates that always fall on the same day of the week within a given year.
Origins of Weekday Names
| Day | Origin |
|---|---|
| Sunday | Sun's day (Sol) |
| Monday | Moon's day (Luna) |
| Tuesday | Tiw/Mars (god of war) |
| Wednesday | Woden/Mercury (messenger god) |
| Thursday | Thor/Jupiter (god of thunder) |
| Friday | Frigg/Venus (goddess of love) |
| Saturday | Saturn (god of agriculture) |
Fun Fact
The 7-day week has been used for thousands of years, with origins in ancient Babylon. It was based on the seven celestial bodies visible to the naked eye: the Sun, Moon, Mars, Mercury, Jupiter, Venus, and Saturn.
Frequently Asked Questions
How can I find out what day of the week a date falls on?
Enter any date in the calculator above, and it will instantly tell you the day of the week. This works for any date in history or the future, making it perfect for planning events or looking up historical dates.
What day of the week was I born on?
Enter your birth date in the calculator to find out. Fun fact: There's a superstition that children born on certain days have different personalities - 'Monday's child is fair of face, Tuesday's child is full of grace...'
Why does the same date fall on different days each year?
Because a regular year has 365 days (52 weeks + 1 day), each date shifts forward by one day of the week annually. In leap years, dates after February shift by two days. This is why holidays like Christmas fall on different days each year.
How do I calculate the day of the week mentally?
The Doomsday Algorithm, created by mathematician John Conway, allows you to calculate any day mentally. It uses 'anchor dates' that always fall on the same weekday within a year (like 4/4, 6/6, 8/8, 10/10, 12/12). With practice, you can determine any day in seconds.