Day of Week Calculator

The Gregorian calendar, introduced by Pope Gregory XIII in 1582, is the most widely used civil calendar in the world today. It refined the earlier Julian calendar to more accurately align the calendar year with the solar year, reducing drift over centuries.

Why Seven Days?

The seven-day week has ancient roots, tracing back to Babylonian astronomy and later adopted by Jewish, Christian, and Islamic traditions. The Romans named days after the seven classical planets (Sun, Moon, Mars, Mercury, Jupiter, Venus, Saturn). In English, most names were later replaced with equivalents from Norse mythology.

Common Uses

• Planning events and scheduling meetings
• Historical research and genealogy
• Verifying birthdays, anniversaries, and holidays
• Checking what day you were born

To calculate the exact span between two dates, try our Date Difference Calculator.