How Was The Calendar Invented?
Summary
TLDRThis 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.
Outlines
📅 The Origin and Evolution of the Gregorian Calendar
This paragraph delves into the history and reasons behind the Gregorian calendar's establishment by Pope Gregory XIII in 1582. It discusses the calendar's purpose, particularly the need to align Easter with the spring equinox, and the adjustments made by Aloysius Lilius to correct the discrepancy. The summary also touches on the calendar's adoption by different countries over time, including Russia's late adoption after the October Revolution. The paragraph explains the leap year system of the Gregorian calendar, which is more accurate in reflecting the Earth's revolution around the Sun, and contrasts it with the Julian calendar's simpler leap year rule.
Mindmap
Keywords
💡Gregorian Calendar
💡Julian Calendar
💡Leap Year
💡Solar Cycle
💡Spring Equinox
💡Aloysius Lilius
💡Daylight Saving Time
💡October Revolution
💡Anno Domini
💡Common Era
💡Lunar Calendar
Highlights
The Gregorian calendar was implemented by Pope Gregory the thirteenth in 1582 to correct the date of Easter.
Easter's traditional date was the first Sunday after the first full moon following the spring equinox, which was drifting out of sync with the solar event.
Italian scientist Aloysius Lilius was commissioned to fix the calendar discrepancy to ensure the correct celebration of Christ's rebirthday.
The switch to the Gregorian calendar caused the Catholic world to jump forward by 10 days.
Non-Catholic countries took hundreds of years to adopt the Gregorian calendar, with Russia switching after the October Revolution in 1917.
The Gregorian Calendar's accuracy comes from its revised approach to leap years, including exceptions for years divisible by 100 but not 400.
The Earth's revolution around the sun is not a perfect 365 days but includes an additional 5 hours, 48 minutes, and 46 seconds.
Before Julius Caesar, the Roman calendar was manipulated for political reasons, affecting the length of years.
Julius Caesar standardized the calendar with 365 days per year and an extra day every four years, known as the Julian calendar.
The Julian calendar's average year was 11 minutes and 14 seconds too long, an error that became evident over centuries.
Caesar's birth month was renamed July in his honor after he reformed the calendar.
The year count starts from 753 in the Roman calendar, as determined by Christian Monk Dionysius Exiguus, leading to the use of BC and AD.
In academia, BCE (Before Common Era) and CE (Common Era) are used instead of BC and AD for neutrality.
The Gregorian Calendar is preferred for predicting seasonal changes due to its regularity, despite a minor inaccuracy that will become significant in 4909.
The Julian calendar is still used by some, offering a humorous suggestion to switch and retry new year's resolutions.
Different cultural calendars rely on lunar cycles rather than solar, impacting the dates of seasons and events.
The video invites viewers to share their experiences with different calendars and whether they use the Gregorian calendar.
Transcripts
Happy new year?
Guys that’s in like a week.
Oh right, I’m on the Julian Calendar.
Good day everyone, Julian here for DNews.
Have you ever wondered why the calendar is the way it is?
What drove us in the western world to have a 365 day year?
Turns out it’s an interplay between astronomy, religion, and history.
The calendar we use right now is the Gregorian calendar, so named because it was implemented
by Pope Gregory the thirteenth in 1582.
Why would the pope be interested in the calendar?
[[*RE-TRACKED on 12/18 - Cars have faces shoot*]]Well Easter was traditionally supposed to fall
on the Sunday after the first full moon after the spring equinox, March 21st, but it had
started slipping later and later behind the solar event.
Gregory was worried they were missing Christ’s rebirthday, so he commissioned italian scientist
Aloysius Lilius to fix it and make sure they were on Jesus’ good side.
When they made the switch, the catholic world jumped forward a full 10 days.
And you thought daylight savings was bad.
Many non-catholic countries wouldn’t adopt the Gregorian calendar for hundreds of years
still.
Russia switched after their October revolution in 1917, which under the new system, technically
began in November.
The reason the Gregorian Calendar is more accurate with our solar cycle is because it
changed how we approached leap years.
It still has a leap year every 4 years, like the Julian Calendar, except for years that
are divisible by 100, except except for years that are divisible by 400.
So 2000 was a leap year, but 2100 will not be.
Why this wonky system for leap years?
As it turns out, our revolution around the sun is not a perfect 365 days, but 365 days,
5 hours, 48 minutes and 46 seconds.
Before Julius Caesar became emperor the calendar was all over the place, literally being manipulated
by the roman high priest for political reasons.
Sometimes years were lengthened to keep allies in office, sometimes they were shortened to
kick rivals out quicker.
Julius Caesar put a stop to that by standardizing the Julian calendar.
Introduced in 45 BCE, or what to the romans was 709 as they counted years from the founding
of the city of Rome.
His calendar had 365 days every year with an extra day every 4.
It still made the average year length 11 minutes and 14 seconds too long, but that wouldn’t
be evident until hundreds of years passed.
To honor him for reforming the calendar, the roman senate changed the name of Caesar's
birth month to July.
They’d honor him again a year later by murdering him on the infamous ides of March
I always wondered, if Caesar could change the calendar willy nilly, why didn’t he
just get rid of March?
Way to drop the ball, Caesar.
The reason we’re in the year 2015 though and not 2768 is because in 525 Christian Monk
Dionysius Exiguus determined that Jesus was born in the roman year 753, and started counting
over again from there.
Because of him we get the terms BC for before Christ, and AD, which does not stand for After
Death but actually Anno Domini, which in Latin means “The Year of Our Lord.”
In the academic and scientific communities, to keep things neutral and welcoming to people
of all faiths, you’ll often see the terms BCE and CE for Before Common Era and Common
Era.
Of course the Gregorian Calendar is far from the only calendar in use around the world
today.
Many calendars from cultures with less pronounced seasons actually rely on the cycles of the
moon instead of the Sun.
But for predicting the change of seasons, equinoxes, solstices, and when certain constellations
will be visible, the Gregorian is the one we prefer for its regularity.
At least until 4909, when it’ll be a day ahead.
If you already blew it on your new years resolution, I’d say switch to the Julian calendar and
try again next week.
But first check out Catie’s video on what you did wrong over here.
I’ve never lived by a different calendar but I’m sure a lot of you out there watching
do.
What’s it like going by a system where the seasons aren’t the same dates each year?
Do you use the gregorian calendar too?
Let us know in the comments, and I’ll see you next time on DNews.
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