Day of the Week Calculator

Find the weekday for any date and view helpful calendar facts

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Day of the Week Calculator

Enter a date to find what day of the week it falls on, plus quick calendar facts.

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ISO 8601

The International Organization for Standardization (ISO) maintains ISO 8601, an international standard for exchanging date and time data. The internationally recognized method of conveying the day of the week commonly uses Zeller's congruence—an algorithm for calculating the weekday for a given date.

Monday is the official first day of the week according to ISO 8601.

Gregorian Calendar

The Gregorian calendar, named after Pope Gregory XIII, is the modern civil calendar. It aligns with the solar year while months loosely reflect lunar cycles.

Where Do Their Names Come From?

Most weekday names derive from Roman and Norse mythology, carried into modern languages. For instance, Sunday stems from the Sun (Sol), Monday from the Moon (Luna), Tuesday from Mars, Wednesday from Mercury, Thursday from Jupiter, and Friday from Venus. Similar etymologies appear worldwide, such as Japanese "kinsei" (Venus) + "yobi" (day) for Friday.

Trivia About Each Day

Monday

  • Statistically associated with higher chances of stock market gains in the U.S.
  • The only weekday that is an anagram of "dynamo".
  • People often report more complaints on Mondays than other weekdays.
  • Average weight can be highest on Mondays.

Tuesday

  • Often cited as the most productive workday.
  • Many job applications are submitted on Tuesdays.
  • Black Tuesday (Oct 29, 1929) marked the U.S. stock market crash.

Wednesday

  • Known as "Hump Day"—the midpoint of the workweek.

Thursday

  • Maundy Thursday commemorates the Last Supper in Christian tradition.
  • "Thirsty Thursday" is a colloquial early start to the weekend.

Friday

  • Friday the 13th is widely considered unlucky in some cultures.
  • In the U.S., "Black Friday" is the heavy-shopping day after Thanksgiving.

Saturday

  • A common day of rest and observance in various countries.
  • Official voting day in Australia and New Zealand.

Sunday

  • The day of rest and worship in Christianity.
  • Months beginning on Sunday include a Friday the 13th.