How Was The Calendar Invented?

Summary

This DNews episode explores the history and significance of the Gregorian calendar, introduced by Pope Gregory XIII in 1582 to correct the drift of Easter from the spring equinox. It explains the calendar's leap year system and its accuracy relative to the solar cycle. The video also touches on the Julian calendar, the origin of our current year numbering, and alternative calendar systems, concluding with a humorous suggestion to switch to the Julian calendar for a second chance at New Year's resolutions.

Takeaways

• 📅 The Gregorian calendar is the most widely used civil calendar today, named after Pope Gregory XIII who introduced it in 1582.
• 🌕 The calendar system was reformed to ensure that Easter, traditionally celebrated on the first Sunday after the first full moon following the spring equinox, would not drift out of alignment with the lunar cycle.
• ⏭️ When the Gregorian calendar was adopted, the Catholic world had to jump forward by 10 days to correct the accumulated discrepancy.
• 🌐 The adoption of the Gregorian calendar was not universal; some countries, like Russia, only switched in the 20th century.
• 🔢 The Gregorian calendar refines the leap year system, with a leap year occurring every 4 years except for years divisible by 100, unless they are also divisible by 400.
• 🌞 Our solar year is not exactly 365 days; it's approximately 365.2425 days, which is why the leap year adjustments are necessary to keep the calendar aligned with the seasons.
• 📚 Before Julius Caesar, the Roman calendar was inconsistent and subject to political manipulation by the high priest.
• 🎉 The Julian calendar, introduced by Julius Caesar in 45 BCE, established a more standardized system with a leap year every four years.
• 🗓 The discrepancy in the Julian calendar's alignment with the solar year became noticeable over centuries, leading to the need for further reform.
• 📜 The current year numbering system, with AD and BC, was established by Christian monk Dionysius Exiguus in 525, who calculated the year of Jesus's birth as 753 in the Roman calendar.
• 🌐 In academic and scientific contexts, BCE (Before Common Era) and CE (Common Era) are used to avoid religious connotations and to be more inclusive.
• 🌟 The Gregorian calendar is preferred for predicting astronomical events due to its regularity, despite a minor inaccuracy that will become significant only in the year 4909.

Q & A

What is the Julian Calendar?

The Julian Calendar is the calendar introduced by Julius Caesar in 45 BCE, which had 365 days every year with an extra day added every four years to account for the slight discrepancy between the solar year and the calendar year.

Why was the Gregorian Calendar introduced?

The Gregorian Calendar was introduced by Pope Gregory XIII in 1582 to correct the drift of the date of Easter and to better align the calendar with the solar year, as the Julian Calendar was slightly too long over time.

What was the significance of the spring equinox in determining the date of Easter?

Easter is traditionally celebrated on the Sunday after the first full moon following the spring equinox, which is around March 21st. The Gregorian Calendar was adjusted to ensure that this date did not drift too far from the solar event.

How did the implementation of the Gregorian Calendar affect the date?

When the Gregorian Calendar was implemented, the Catholic world jumped forward by 10 days to realign with the solar year.

Which country was one of the last to adopt the Gregorian Calendar?

Russia was one of the last countries to adopt the Gregorian Calendar, doing so after the October Revolution in 1917.

What is the difference in the leap year calculation between the Julian and Gregorian Calendars?

While both calendars have a leap year every four years, the Gregorian Calendar excludes years divisible by 100 unless they are also divisible by 400, making it more accurate.

How does the Earth's revolution around the Sun affect the need for a leap year?

The Earth's revolution around the Sun is not exactly 365 days but approximately 365 days, 5 hours, 48 minutes, and 46 seconds, which necessitates the addition of a leap day to keep the calendar year aligned with the solar year.

Why did the Roman Senate name July after Julius Caesar?

The Roman Senate named July after Julius Caesar to honor him for his reform of the calendar with the introduction of the Julian Calendar.

What does AD stand for and why was it introduced?

AD stands for Anno Domini, which means 'The Year of Our Lord' in Latin. It was introduced by Christian Monk Dionysius Exiguus in 525 to count years from the birth of Jesus, which he calculated to be in the Roman year 753.

Why do academic and scientific communities often use BCE and CE instead of BC and AD?

BCE (Before Common Era) and CE (Common Era) are used to maintain neutrality and to be more inclusive of people of all faiths, avoiding the religious connotations of BC (Before Christ) and AD (Anno Domini).

What is the expected accuracy of the Gregorian Calendar until when?

The Gregorian Calendar is expected to remain accurate until the year 4909, after which it will be a day ahead of the solar year.