Day of the Week Calculator
Use the calculator below to find the day of the week of any date. It also gives out a few facts as well as the calendar of the month.
ISO 8601
The International Organization for Standardization (ISO) defines ISO 8601, the global standard used for formatting and exchanging date and time data. Although widely adopted across the world, some regions still follow different systems.
ISO 8601 also standardizes how weekdays are determined. It uses a mathematical method called Zeller's Congruence, developed by Christian Zeller, to calculate the day of the week for any given date. According to this standard, Monday is considered the first day of the week.
Gregorian Calendar
The Gregorian Calendar, introduced by Pope Gregory XIII, is the calendar system used worldwide today. It is based on the Earth's motion around the Sun (one year) and the Moon's cycle (one month).
Ancient civilizations relied heavily on celestial bodies to track time. Over centuries, these observations were refined into the accurate calendar system we use today.
Origin of Weekday Names
The names of the days of the week mainly come from Roman mythology and celestial bodies. These names spread across cultures and languages over time.
- Sunday → Sun (Sol)
- Monday → Moon (Luna)
- Tuesday → Mars
- Wednesday → Mercury
- Thursday → Jupiter
- Friday → Venus
- Saturday → Saturn
These names influenced many global languages. For example, in Japanese, Friday relates to Venus, while Tuesday translates to "fire day" (Mars). In India, Thursday is often called Guruvara, linked to Jupiter.
Interesting Facts About Each Day
Monday
- Stock markets are statistically more likely to rise.
- People tend to feel more stressed compared to other days.
- It is often when people weigh the most.
Tuesday
- Considered the most productive workday.
- Most job applications are submitted on this day.
- Famous event: Black Tuesday (1929 stock market crash).
Wednesday
- Known as "Hump Day" — midpoint of the workweek.
- A symbolic turning point toward the weekend.
Thursday
- Maundy Thursday occurs before Easter in Christianity.
- "Thirsty Thursday" is popular among students.
Friday
- Friday the 13th is considered unlucky in many cultures.
- Black Friday marks major shopping sales in the U.S.
- Good Friday honors the crucifixion of Jesus.
Saturday
- Official rest day in Israel.
- Common election day in Australia & New Zealand.
- In Sweden, children traditionally eat candy only on Saturdays.
Sunday
- Observed as a day of rest and worship in Christianity.
- Many banks and businesses remain closed.
- Super Bowl Sunday is one of the biggest sporting events.