Join the Unexplained Mysteries community today! It's free and setting up an account only takes a moment.

# Gregorian Calendar Question

## Recommended Posts

So been reading up about different cultures and calendars and found something a little confusing. I was always thought that when the calendar switched to Gregorian in the 1500’s there were 11 days lost. But a friend of mine told me 8 years were lost. Did an internet search and found not much that confirms this. So why did we lose 11 days or 8 years.

• 1

##### Share on other sites

Eleven days is the correct answer.

• 1
• 1

##### Share on other sites
13 minutes ago, Damien99 said:

So been reading up about different cultures and calendars and found something a little confusing. I was always thought that when the calendar switched to Gregorian in the 1500’s there were 11 days lost. But a friend of mine told me 8 years were lost. Did an internet search and found not much that confirms this. So why did we lose 11 days or 8 years.

When Julius Caesar created the Julian calendar a little over 2000 years ago he set the length of the year at 365.25 days - one leap year every four years (or 100 every 400 years). The problem is that the year isn't 365.25 days long, it's a little bit shorter than that. By the 1500s the Julian calendar had included 11 days more than were necessary to reach the time of the year we were at.

The Gregorian calendar removes three of those leap years in a 400 year period, giving us 97 leap years every 400 years. That means an average year length of 365.2425 days. This is much closer to the actual length of the year (365.2422 days IIRC), meaning it'll take about 3000 years to be out by even a single day.

• 2
• 1

##### Share on other sites
8 minutes ago, Peter B said:

When Julius Caesar created the Julian calendar a little over 2000 years ago he set the length of the year at 365.25 days - one leap year every four years (or 100 every 400 years). The problem is that the year isn't 365.25 days long, it's a little bit shorter than that. By the 1500s the Julian calendar had included 11 days more than were necessary to reach the time of the year we were at.

The Gregorian calendar removes three of those leap years in a 400 year period, giving us 97 leap years every 400 years. That means an average year length of 365.2425 days. This is much closer to the actual length of the year (365.2422 days IIRC), meaning it'll take about 3000 years to be out by even a single day.

So we lost 11 days? Not sure if your response answered my question

##### Share on other sites
12 minutes ago, Damien99 said:

So we lost 11 days? Not sure if your response answered my question

The longer answer: The purpose of the calendar is to align our activities with particular times of the year. So a calendar helps farmers know when it's time to sow and reap, and so on. Therefore a calendar is only useful if 1 January occurs at the same time in the Earth's annual cycle, year after year, reliably. If the length of the year on a calendar is different from the actual length of the year provided by the Earth's motion around the Sun, then people relying on the calendar to do things on a certain date will be doing them at the wrong time.

The cross-check for this comes from looking at the night sky and seeing where the various constellations are and when they rise and set. Therefore, on 1 January when the Julian calendar started astronomers knew exactly where the constellations were.

But on average each calendar year was slightly longer than the actual amount of time it took for the Earth to go around the Sun. In the 1500 years after Julius Caesar inaugurated his calendar the Julian calendar had slipped out of alignment by a total of 11 days. People would look at the calendar and say, "The calendar says that today is 1 January, but according to the star charts the Romans made 1500 years ago the night sky looks like it does on 12 January." {I don't know if this is exactly how the arguments went, but it explains the effect.}

If you do nothing about this then eventually the calendar becomes useless for aligning activities with particular times of the year (remember, the original purpose of the calendar).

So the solution was to (a) develop a new calendar which more closely matched the actual length of the year (remove three leap years every 400 years), and (b) get the calendar back into alignment with the actual year by decreeing that the day after 1 January would be 13 January (that is, skipping 11 days). {It didn't actually happen then, but I'm just using those dates for illustrative purposes.}

Now this decree wasn't universally accepted at the time - because the decree was promulgated by the Pope it was ignored in a number of non-Catholic countries. Britain didn't make the correction until the 18th century, and Russia not until after the Communist Revolution.

Does this help?

• 1
• 3

##### Share on other sites
9 hours ago, Damien99 said:

But a friend of mine told me 8 years were lost.

I've also recently seen the claim that 8 years were lost. It's not correct. As Peter B has correcly said (and as you correctly suspected) it was 11 days.

I suspect that the figure of 8 years comes from the difference between the Gregorian calendar and the Ethiopian calendar.

The Ethiopian calander is a version of the Coptic calendar, which itself is based on the Egyptian calendar. It is the official calendar of Ethiopia and of the Ethiopian Orthodox Church. It  has 13 months in a year and differs from the Gregorian calendar by 7-8 years, which is where I suspect your friend got the figure from.

It is not due to any time being lost, but on different calculations as to the date of the birth of Christ.

Rather than the Gregorian calendar having lost 8 years it is actually 7-8 years ahead (depending on the time of year).

On 11th September 2020 Ethiopia will celebrate their New Year and it will be 2013 in their calendar.

• 1

Thank you all

##### Share on other sites
Posted (edited)
On 6/5/2020 at 7:41 AM, Waspie_Dwarf said:

I've also recently seen the claim that 8 years were lost. It's not correct. As Peter B has correcly said (and as you correctly suspected) it was 11 days.

I suspect that the figure of 8 years comes from the difference between the Gregorian calendar and the Ethiopian calendar.

The Ethiopian calander is a version of the Coptic calendar, which itself is based on the Egyptian calendar. It is the official calendar of Ethiopia and of the Ethiopian Orthodox Church. It  has 13 months in a year and differs from the Gregorian calendar by 7-8 years, which is where I suspect your friend got the figure from.

It is not due to any time being lost, but on different calculations as to the date of the birth of Christ.

Rather than the Gregorian calendar having lost 8 years it is actually 7-8 years ahead (depending on the time of year).

On 11th September 2020 Ethiopia will celebrate their New Year and it will be 2013 in their calendar.

But would we not calculate 11 days lost per year since the introduction

The number of days lost in a year due to the shift into Gregorian Calendar is 11 days. For 268 years using the Gregorian Calendar (1752-2020) times 11 days = 2,948 days. 2,948 days / 365 days (per year) = 8 years”.

Or is my math wrong

Edited by Damien99

##### Share on other sites
40 minutes ago, Damien99 said:

But would we not calculate 11 days lost per year since the introduction

The number of days lost in a year due to the shift into Gregorian Calendar is 11 days. For 268 years using the Gregorian Calendar (1752-2020) times 11 days = 2,948 days. 2,948 days / 365 days (per year) = 8 years”.

Or is my math wrong

I haven't a clue what you are trying to calculate.

I'm not sure you understand what is meant by 11 days being lost. It's actually rather simple, the "missing days" were simply removed from the calendar, there is no need to calculate anything.

The Julian calendar did not correctly calculate leap years, as a result it was out of sync with the actual date by 11 days. These days were simply missed off of the calendar to bring the new, Gregorian calendar into sync with the actual time of year.

For example, England adopted the Gregorian calendar in 1752. 1752 was a leap year and so should have had 366 days, but in England that year had only 355 days. Wednesday 2nd September was followed by Thursday 14th September, hence the missing 11 days.

Other nations adopted the Gregorian calendar at different times.

##### Share on other sites
Posted (edited)

Read my post again. The Julian calendar wasn't out by 11 days each year, but by 11 days in total.

The Julian calendar provided for a year of 365.25 days. The actual length of a year is around 365.2422 days.

365.25 - 365.2422 = 0.0078 days error per year.

The error built up between the time of Julius Caesar and Pope Gregory, about 1500 years.

1500 * 0.0078 = 11.7 days

Edited by Peter B
• 1

##### Share on other sites
Posted (edited)
19 hours ago, Peter B said:

Read my post again. The Julian calendar wasn't out by 11 days each year, but by 11 days in total.

The Julian calendar provided for a year of 365.25 days. The actual length of a year is around 365.2422 days.

365.25 - 365.2422 = 0.0078 days error per year.

The error built up between the time of Julius Caesar and Pope Gregory, about 1500 years.

1500 * 0.0078 = 11.7 days

I see but the current claim is that it’s supposed to be 11 days a year and not just a 1 time 11 days? So where is the confusion coming from?

it seems if from a scientist named Paolo Tagaloguin. I have never heard of him and searches come up empty. His twitter account has been removed

Edited by Damien99

##### Share on other sites
5 minutes ago, Damien99 said:

I see but the current claim is that it’s supposed to be 11 days a year and not just a 1 time 11 days?

Not it isn't, that's just more nonsense you have made up.

There are literally dozens of websites that explain the 11 missing days. Stop being lazy, actually learn something. It's easy, just Google "11 missing days Gregorian". Pick a site. Read it. Repeat this process until you understand.

6 minutes ago, Damien99 said:

So where is the confusion coming from?

Where it always comes from, your lack of knowledge and compression of simple subjects.

##### Share on other sites
12 minutes ago, Waspie_Dwarf said:

Not it isn't, that's just more nonsense you have made up.

There are literally dozens of websites that explain the 11 missing days. Stop being lazy, actually learn something. It's easy, just Google "11 missing days Gregorian". Pick a site. Read it. Repeat this process until you understand.

Where it always comes from, your lack of knowledge and compression of simple subjects.

I am not making it up there are tons of news articles claiming that Paolo Tagaloguin claimed we have calculated it wrong

##### Share on other sites
35 minutes ago, Damien99 said:

I am not making it up there are tons of news articles claiming that Paolo Tagaloguin claimed we have calculated it wrong

Then provide a link to one.

##### Share on other sites

Paolo Tagaloguin is claiming that the MAYAN calender is being interpreted wrong.

His calculation, which you dishonestly claimed as your own, is based on a wrong assumption, as explained by Peter B and myself, that is why he removed his account.

You are confusing two different things, the change from the Julian to the Gregorian calendar and a total separate story about the Mayan calendar.

##### Share on other sites
Posted (edited)
9 minutes ago, Waspie_Dwarf said:

Then provide a link to one.

Probably what he is referring to.

It lists the 8 year calculation.  Still incorrect,  but it was in print

Edited by Jarocal

##### Share on other sites

Incidentally whilst Paolo Tagaloguin is a scientist, he is actually a biologist so has no more knowledge of calendars than anyone else.

His entire calculation is based on the fact that the Julian calendar and the Gregorian calendar differ by 11 days a year and so this is actually 2012. That is nonsense. The Julian calendar and the Gregorian calendar differed by 11 days once and once only. Those 11 days were removed from the calendar and the discprepenesies were solved.

• 1

##### Share on other sites
5 minutes ago, Jarocal said:

Probably what he is referring to.

It lists the 8 year calculation.  Still incorrect,  but it was in print

Thanks, I looked it up myself.

On a 1 to 10 scale of wrongness Tagaloguin scores about a 20. He should stick to biology.

• 1

##### Share on other sites
2 minutes ago, Waspie_Dwarf said:

Incidentally whilst Paolo Tagaloguin is a scientist, he is actually a biologist so has no more knowledge of calendars than anyone else.

His entire calculation is based on the fact that the Julian calendar and the Gregorian calendar differ by 11 days a year and so this is actually 2012. That is nonsense. The Julian calendar and the Gregorian calendar differed by 11 days once and once only. Those 11 days were removed from the calendar and the discprepenesies were solved.

I agree.

##### Share on other sites
8 minutes ago, Waspie_Dwarf said:

Paolo Tagaloguin is claiming that the MAYAN calender is being interpreted wrong.

His calculation, which you dishonestly claimed as your own, is based on a wrong assumption, as explained by Peter B and myself, that is why he removed his account.

You are confusing two different things, the change from the Julian to the Gregorian calendar and a total separate story about the Mayan calendar.

I never claimed it as my own? And according to what he wrote he claims 8 years. Everytime i try searching the 11 days to 8 years all that comes up is news articles with his claims we are really in 2012.

##### Share on other sites
Posted (edited)
2 minutes ago, Damien99 said:

I never claimed it as my own? And according to what he wrote he claims 8 years. Everytime i try searching the 11 days to 8 years all that comes up is news articles with his claims we are really in 2012.

He is in error. As Waspie pointed out the 11 day adjustment needed occur only once, not annually.

It could be construed as an exercise of Mathterbation.

Edited by Jarocal

##### Share on other sites
4 minutes ago, Jarocal said:

He is in error. As Waspie pointed out the 11 day adjustment needed occur only once, not annually.

It could be construed as an exercise of Mathterbation.

That’s why I am having trouble understanding why it’s only a 1 time 11 day thing and not yearly to me it would be yearly

##### Share on other sites
23 minutes ago, Damien99 said:

That’s why I am having trouble understanding why it’s only a 1 time 11 day thing and not yearly to me it would be yearly

Because the adjustment was only needed in the julian/gregorian switch. Hence one time.

##### Share on other sites
9 minutes ago, Jarocal said:

Because the adjustment was only needed in the julian/gregorian switch. Hence one time.

Is there anywhere I can read more I for action about all this

##### Share on other sites
7 minutes ago, Damien99 said:

Is there anywhere I can read more I for action about all this