Why 11 days disappeared in 1752 | Hacker News Reader

Why 11 days disappeared in 1752

augustachronicle.com

134 pointsmortenjorck97 comments

The article mentions this, but for those who just read the comments, the missing eleven days was not the only weird thing about 1752. Prior to this year, New Year's Day in England was observed on March 25 (the Feast of the Annunciation). So, for example, March 24, 1741 would be followed by March 25, 1742. This was known as "Annunciation dating" and was common throughout Europe during the Middle Ages. By the 1700s most of Europe had moved New Year's Day to January 1 (known as "circumcision dating" because it fell on the Feast of the Circumcision), but England had stayed on the old system.

In 1750, Parliament had had enough and harmonized the calendar with the rest of Europe. By decree, 1752 would begin on January 1 the day after December 31, 1751. This meant that January and February of 1751 did not exist! In fact, in England 1751 had only 288 days.

Since England's calendar was unusual by European standards people had adapted "dual dating" techniques to avoid confusion [1]. The most common was to write a date with two years, one on top of the other. So you would say January 15, 1748/49, with the 48 on top of the 49.

And 1751/52 weren't the only weird years in history. When the Julian calendar was adopted, the previous calendar had drifted so far from the seasons that two leap months needed to be added, which made the year 46 BC 445 days long.

[1]: https://en.wikipedia.org/wiki/Dual_dating

[Edited to correct Assumption to Annunciation.]

Small nitpick: it's "Annunciation", not "Assumption". Both feast days are associated with the Blessed Virgin Mary, but Assumption Day falls on 15th August whereas the Annunciation is celebrated on 25th March.

You are correct, my fingers got ahead of my brain. :)

> By the 1700s most of Europe had moved New Year's Day to January 1 (known as "circumcision dating" because it fell on the Feast of the Circumcision)

Do we know why this happened? In a world context, beginning the year in spring is normal; beginning it in the middle of winter is very weird indeed.

And it's not like this was a restoration of an older tradition. Four of the months are still literally named on the assumption that the first month of the year is March.

It kind of was the restoration of an older tradition: http://www.britannica.com/story/why-does-the-new-year-start-... though it is apparently not very clear who exactly started it and why that person did it.

March 25th is roughly the spring equinox. January 1st is roughly the shortest day of the year. Both seem like reasonable choices.

December 21st is the shortest day of the year.

Sometimes. Sometimes it's the 22nd. Neither of which are a long way from January 1st. Hence "roughly".

> In a world context, beginning the year in spring is normal; beginning it in the middle of winter is very weird indeed.

The character of the seasons is rather local. For example take the Greek legend of Persephone and Demeter and the Sumerian legend of Dumuzid and Inanna. Both explain the seasons by a god being trapped in the underworld for half the year, but the Greeks considered winter the dead time while for the Sumerians it was summer.

I seem to recall that the myth of Persephone is generally taken to be an import the Greeks brought with them when they arrived in Greece, since the weather patterns it describes don't really correspond to Greek weather.

> Four of the months are still literally named on the assumption that the first month of the year is March.

Right. Also, with March being the first month of the year, the variable-length month becomes the last one. On leap years, you add a day at the end of the year. Which is reasonable, unlike the current situation.

They had a perfectly sane calendar system and somebody just had to break it.

The Solstice is when the days start getting longer again. I feel very time crunched at that time of year. The ancients probably did not use precise clocks to detect Solstice. Its farthest south sunset on the horizon and easy to observe when sunsets begin moving north again.

> The ancients probably did not use precise clocks to detect Solstice.

This is most definitely false; tracking the solstices with pinpoint accuracy was a goal of ancient cultures since before the beginning of recorded history.

But the tax year stayed 365 days and so it now starts on April 6th, the 11 days comes from correcting the drift between the Julian and Gregorian calendars. Russia switched later and had to add more days.

Calendars are such ugly hacks. We should fix the year so we can design a properly engineered calendar... what would it take to shift Earth into another orbit?

I suspect do that would be more acceptable than removing day light saving.

A lot of energy. Probably more than the world uses in an entire year, but I'm going to leave it as an exercise for the reader.

(Kind of reminds me of the analysis of how much energy the death star would require to destroy an entire planet, and what kind of energy density would be required to do it from a facility that is the size of a "small moon.")

I mean, it really depends on what's meant by "another orbit". Even the most minuscule change is "another orbit".

> Probably more than the world uses in an entire year, but I'm going to leave it as an exercise for the reader.

My back of the napkin estimate says about 7 orders of magnitude more, just to eliminate leap years.

I mean, at some point (hopefully) humans will be living on more than one planetary body in the solar system.

Once you have people on Mars and Earth, you're never going to harmonize the two, without shifting both to the same orbit.

So you could just give up on having the planet's orbit define the calendar, design a pleasing civil calendar for your civilization that is probably roughly a Earth year long, but without all the hacks to make it exact or synchronized, and just let your cell phone add a calendar event for when spring, etc starts.

I liked Kodak's division of the year in 13-months with roughly 28 days. Only one month would be different, with 29 or 30 days.

The International Fixed Calendar was a work of elegant beauty and it’s a shame we are not using it.

Plus the Earth is erratic in its movements compared to atomic clocks. When they switched the definition from a fraction of an astronomical day to wavelengths of a particular Cesium photon, they would have to add a leap second a few times a decade. Last year they were considering subtracting a second because the Earth speed up its orbit for unknown causes.

That’s very interesting. In Iran, the New Year still starts with the first day in spring. It makes more sense to me since spring feels like everything starts anew.

In some official places (for instance, Presidential proclamations), dates will still be given counting from July 4, 1776.

> Prior to this year, New Year's Day in England was observed on March 25 (the Feast of the Annunciation).

In the UK, but also here in Canada and in many other Commonwealth countries, the fiscal new year is April 1st. This is why, if you ever wondered.

Something I never see being talked about in these sorts of threads is how Japan switched from the local lunisolar calendar to the Gregorian calendar. In the year 1872 (Meiji 5) the imperial government were paying their officials on a monthly basis, but their finances were in trouble, and the 6th month of the following year (Meiji 6) was a leap month which meant that they would have to budget an extra month's worth of pay for that year. Adopting the Gregorian calendar turned out to be a way out of this problem. As a "bonus", if they adopted it starting 1873 then the 12th month of the current year would only last two days and they could get away with skipping that month's pay completely.

The calendar reform was officially announced on the 9th day of the 11th month of Meiji 5, or 9 December 1872, to take effect 1 January 1873. This understandably caught people off guard, especially since official calendar makers had already started selling calendars for the new year a month earlier.

Caesar switch Europe to a solar calendar after seeing its advantage in Egypt. Egypt likely synced its calendar to when the star Sirius first appears in the dawn sky in July.

This would not be accurate over long periods of time due precession and proper motion.

Sweden did an... interesting version of calendar change. Like Britain, we stuck with the Julian calendar for quite some time. Then we decided to catch up with the Gregorian calendar by omitting leap days, starting from 1700 (this would have taken 40 years!). To make matters worse, the scheme was forgotten and 1704 and 1708 were leap years. In 1712, Charles XII decided to sync back to the Julian calendar by having an extra leap day, making a 30-day February, which I think is unique. We then finally went Gregorian by omitting 12 days at the end of February 1753.

Thankfully software didn't exist back then.

There's some oversimplification of things in that even the first countries to adopt the Gregorian calendar (Spain, Portugal, France, Poland, Italy, Catholic Low Countries, Luxemburg, and their colonies in 1582), lost 10 days in the transition. They make it seem as if the 11 day discrepancy happened in the relatively short time between the creation of the Gregorian calendar and its adoption in Britain.

Wikipedia is silent on this, but the skipped days are there to make up for the errors in the Julian calendar dating back to the beginning of the common era, and not merely the transition as decreed by Pope Gregory.

> Wikipedia is silent on this, but the skipped days are there to make up for the errors in the Julian calendar dating back to the beginning of the common era, and not merely the transition as decreed by Pope Gregory.

And Pope Gregory did this so as to put the equinoxes and solstices back to where they 'should' be: on the 20-22st of their respective months.

Most importantly (to the Pope/Catholics/Christians) was the March equinox, the first day of spring, because that determined when Passover/Easter was supposed to be celebrated.

Jesus of Nazareth was crucified on Passover (Friday):

> So sure enough, when we come to the Gospels, what does Jesus do? When He goes to Jerusalem to die, does He do it at the Feast of the Day of Atonement? No. Does He do it at the Feast of Hanukkah? He could have died at Hanukkah. No. Does He do it at their New Year Festival? No. When does He choose to go down Jerusalem? At Passover, and there’s a reason. He, of course, knows the Scriptures, but as a Jew He’s going to fulfill even their traditions about the fact that the Messiah was going to come on Passover night, and He’s going to die just like the Passover lamb died.

[…]

> The first Passover started in Egypt with slavery to pharaoh and it ends in the Holy Land. But Jesus’s new Passover—watch this—starts in the Holy Land and where does it end? Where does it lead? Not to the earthly promised land, but to where? To Heaven.

> Because, see, ultimately the Passover is a shadow of what Christ is going to accomplish. He doesn’t come to set us free from political slavery to pharaoh. He comes to set us free from the slavery of sin. […]

* https://catholicproductions.com/blogs/blog/passover-and-the-...

So to find the 'proper' day of Passover/Easter, one starts with the (northern hemisphere) Spring Equinox, move forward to the first full moon, and the first Sunday after it is Easter Sunday:

* https://en.wikipedia.org/wiki/Computus

If the day of your equinox is off, so is the celebration of your salvation from sin.

I ran a weekly trivia challenge when I was in high school. I'd offer up an obscure question, and the first to answer it won a free pizza. The one question that remained unanswered at the end of the year was, "what happened on September 10th, 1752 in Britain?"

At the end of the year, I revealed the answer to that one question that had remained unanswered. Nothing had happened that day, as it didn't exist. Afterwards I had to explain the transition to from a Julian calendar to a Gregorian one to a very miffed group of trivia players.

I can't believe I'd never heard of this before, but apparently it's true. Some people born before 1753 were considered to have been born in two years simultaneously.

https://genealogy.stackexchange.com/questions/132/what-is-a-...

Crazier still....

> Imagine – a person could have been married on April 26, 1710 and died on Feb 2, 1710.

(Because the new year began on March 25 prior to 1752)

That's crazy for us. But for them the year was from March to February (ok from March 25th to March 24th :D).

Still, dying 2 months before getting married was crazy for them, too.

"What year was George Washington born" makes for a great trivia question; there is no answer.

i think that was 1732

He was born in 1731. In the calendar reforms of 1752, February 1731 retroactively became February 1732. So, when he was 15 years old, he had been born in 1731, but by the time he was 30, he had been born in 1732.

Of course there is, one only needs to specify which calendar one is using when giving the answer. You could answer in the Chinese calendar if you wanted.

I'm trying to describe this without antagonism, forgive me if I fall. But your question to me sounds just like saying, "at what temperature does water freeze?" and claiming there is no answer because Fahrenheit and Celsius both exist.

I feel like the article makes a similar mistake in claiming that certain dates did not exist. They are simply different calendars and the dates existed even if no one called them that date when they happened. It's like saying the 4th of July, 1776 BCE didn't exist - of course it did but nobody called it that at the time.

Just thinking about the number of edge cases if this happened today gives me palpitations.

And I thought this whole daylight saving time thing is ridiculous. Hold my beer, along comes the Church of England.

I believe this is why some parts of Appalachia still celebrate “Old Christmas” on January 6, which is Epiphany for the rest of the Western church. To my knowledge, this doesn’t affect their observance of Easter, which conforms to the Gregorian date.

The different Easter dates are complicated and not necessarily the same question as Julian vs. Gregorian (though there is a connection). Churches might go either way on the two questions independently. For example, modern Greece is the exact opposite of what you describe for Appalachia: Greek Orthodoxy has adopted the Gregorian calendar, and celebrates Christmas on December 25 every year. But it uses a different ("Eastern Christian") method of calculating the date of Easter, which sometimes coincides with Western Easter, but sometimes can differ from the Western method by as much as 4-5 weeks. I don't fully understand it, but it has something to do with: secular calendars, lunar calendars, and how you compute the date for Passover.

It's even more interesting than you say—the Greeks (and some other Orthodox churches) use the Revised Julian Calendar https://en.wikipedia.org/wiki/Revised_Julian_calendar which aligns with the Gregorian calendar for roughly the millenium spanning 1700–2700. To make this work, they had their own skippage of days in 1923.

The Gregorian and Revised Julian calendars agree up to 28 February 2800. The next day, they begin to diverge – 28 Feb 2800 is followed by 29 Feb 2800 in the Gregorian, but 1 March 2800 in the Revised Julian, and from then onwards the Revised Julian Calendar remains one day ahead. In 2900, they pull temporarily back into synch; in that year, the Revised Julian Calendar has a leap year, but the Gregorian doesn't. In the year 3200, they fall out of synch again, and the Revised Julian once again becomes one day ahead of the Gregorian.

I really wonder what the Gregorian-calendar-using parts of the Eastern Orthodox Church are going to do in the year 2800 – assuming they are still around. Will they remember they are supposed to be using the Revised Julian calendar instead of the Gregorian? Or will they decide that being a day ahead of the civil calendar isn't worth the hassle?

Maybe by the year 2800 there will be people living on Mars, and maybe even some of them will be Christians, even Eastern Orthodox Christians. I wonder if they will insist on using the Earth calendar, complete with Earth days of exactly 86,400 seconds, and with the boundary between Earth days shifting awkwardly through the Martian day? Or will they adopt a liturgical calendar based on the Martian sol (which is 2219.6 seconds longer than the Earth day)? Do they use the Martian year of 668 sols, or the Earth year of 355 sols, as their liturgical year? The whole Gregorian vs Julian debate, which is still alive in the Eastern Orthodox Church, makes little sense on Mars.

The whole concept of interplanetary calendars and time keeping will be interesting to see how it's resolved (assuming our species lives long enough for it to matter). It makes the current mess of time zones, daylight savings/summer time and leap seconds seem trivial by comparison. At least the Martian day isn't very different in length from the Earth day, but how will our biology adapt to colonization on a planet where, say, a day is 15 hours or 36 hours?

The original Julian calendar, as developed in pre-Christian ancient Rome, had no concept of Easter. But when Christianity became the state religion, the method of calculating the date of Easter became part of the official calendar. Originally Easter was defined astronomically, based on observation of the Moon; however, that posed problems in that different places might make different observations (depending on variations in astronomical skill, and even weather conditions), resulting in different places celebrating Easter on different dates. In the quest for uniformity, they instead introduced a table-based system for determining the date of Easter, based on a simulation of where the Moon should be instead of its actual location. The simulation is based on ancient astronomy, but is less than completely accurate. Hence the date of Easter depends, not on the actual Moon, but rather on a virtual "ecclesiastical Moon".

And when Pope Gregory reformed the calendar, he didn't just change the leap year calculation, he also changed the calculation of the position of the "ecclesiastical Moon" to try to make it more astronomically accurate (albeit still inaccurate by modern standards). Hence, there are two different methods of calculating Easter, "Julian Easter" and "Gregorian Easter" – the former uses the original Julian solar calendar, and the original ecclesiastical lunar calendar; the later uses both the revised leap year rule, and the modifications to the ecclesiastical lunar calendar as well.

To make it even more complex, when parts of the Eastern Orthodox Church adopted the Gregorian calendar (or strictly speaking the Revised Julian Calendar, which is a slightly different leap year rule which agrees with the Gregorian until 2800), they kept using the Julian calendar (both its leap year rule and the associated ecclesiastical lunar calendar) for calculating the date of Easter. Hence the whole Eastern Orthodox Church celebrates Easter on the same date – which is different from when Western Christians (Protestants and Latin rite Catholics) celebrate it. By contrast, the "New Calendar" part of the Eastern Orthodox Church (e.g. the Church of Greece) celebrates Christmas on the same date as Western Christians, whereas the "Old Calendar" part (e.g. the Russian Orthodox Church) celebrates it on a different date instead.

Almost all orthodox churches, except the Finnish and maybe Estonian, celebrate Easter in the Eastern way. The correctness of this approach is confirmed every year by the Holy Fire, which doesn't follow the new calendar!

I was unaware of the Holy Fire, what a neat tradition.

I used to have some ex-Soviet country co-workers who took their Christmas break in my January, and I'm sure it was the only time of the year they used that calendar in public. Perhaps in part because of the curious people like us have endless questions about it ;)

Wikipedia has an article on the calendar¹, including how and why the movable feasts are calculated.

¹ https://en.m.wikipedia.org/wiki/Eastern_Orthodox_Church_litu...

Most Russians aren't even aware that this is due to the church using a different calendar - as far as they're concerned, "orthodox Christmas" just happens to be on January, 7 (as opposed to "catholic Christmas" on December, 25).

This is further reinforced by January, 7 being a state holiday in Russia - defined directly like that, without any references to the old calendar.

Various Christian festivals seem to have taken over from pagan celebrations. The winter solstice is at a similar time to Christmas, and Easter has pre-Christian meaning too. Taking over Christian festivals seems inevitable in that context.

Well, many churches use old calendar dates in their church calendars, on websites etc, at least in parallel to the new style. I suppose this might be more common in the diaspora.

The Russian Orthodox Church calendar is Julian; but keep in mind that church attendance in Russia is low - only about 15% attend at least monthly (for comparison, the same figure is 45% in US), and 35% never go at all.

Thus, most believers aren't aware of those details even if they self-identify as Orthodox Christian.

This ignorance might be promoted by the coincidence that in 2001 it didn't change. In 1901 it moved from 6th to 7th, and in 2101 it will move from 7th to 8th. A couple of centuries in which it doesn't move is a good time for people to forget that it moves.

It didn't move in 1901 for Russia, because the country was wholly on the Julian calendar back then, and thus Christmas was still on December, 25.

It's an interesting question as to what exactly is going to happen when it's time to move it. As I noted earlier, the Russian law on state holidays explicitly designates January, 7 as Christmas - so that would need to be amended to conform to what the Church says. But, much like in the West, Christmas is not a purely religious holiday in Russia - it's effectively the last day of the New Year holiday week. In theory, individual regions can opt out of it (to reflect their local religious traditions - some are majority Muslim or Buddhist), but none have done that in practice. So, if the question of moving it arises, it will be debated by the society at large, not only by the Orthodox.

Western Christmas is based on the lunar calendar, the first Sunday after the full moon after the vernal equinox.

You mean Easter?

January 7th, not 6th, though the day before Christmas is also celebrated.

And Easter is affected as well. Sometimes they fall under the same weekend, sometimes they don't. This year it's on the 25th of April. I don't know how exactly the weekend is picked.

Easter Sunday is the first Sunday after the paschal full moon.

https://en.wikipedia.org/wiki/Easter#Date

Russian Orthodox Church is so orthodox that is still refuses to recognise this new calendar and uses Julian calendar. So Chrismas happens on Jan 7 and will soon move to Jan 8.

That's not specific to Russian Orthodox church, other orthodox churches do it as well (Balkans, Israel, Ethiopia, Egypt etc).

Not all orthodox churches: Greek and Bulgarian churches are on Gregorian calendar (technically on Revised Julian[1] which is aligned with Gregorian until the year 2800).

[1] https://en.wikipedia.org/wiki/Revised_Julian_calendar

Took even longer in Eastern Europe and the Eastern Orthodox countries.

The last country of Eastern Orthodox Europe to adopt the Gregorian calendar for civil purposes was Greece, only ~100 years ago, at the time under military administration following the 11 September 1922 Revolution, with Wednesday 15 February 1923 being followed by Thursday 1 March 1923.

For anyone looking for an interesting rabbit trail, they may want to read up on Eastern Orthodox calendars and their controversies; specifically, the Revised Julian calendar, which is effectively a more accurate Gregorian calendar.

https://en.wikipedia.org/wiki/Revised_Julian_calendar

I guess these countries still follow the older calendar still for some church activities. This years Easter is yet to to happen in Russia, for example.

This also explains the confusing naming of the two Russian revolutions: The February/March revolution, and the October/November revolution.

I read an essay once by Isaac Asimov about this fact .. and I remember that in russia they hadn't fully switched when he was born, but did before his family immigrated to America. By that time the loss was 13 days, and he ended the essay by saying, "Where are my thirteen days? Give me my thirteen days!"

I was going to bring up how Russia was apparently late to the War of the Third Coalition due to still being on the old calendar, but it turns out to be not true:

http://dcjack.org/kagan%20on%20ulm.html

I have also heard similar (fanciful) stories about the start of WW1, when Russia was still on Julian.

The link just goes to some articles about golf.

Yes, for me too :-(

Here's Google's cached version: https://webcache.googleusercontent.com/search?q=cache:8TiKyG...

They could’ve just skipped adding a day in leap years for like 40 years and avoid the big disruption. Apparently this was considered as one of the proposals but didn’t go through.

Sweden tried to do this. Of course, it meant they would be out of sync with both Julian and Gregorian calendars for 40 years, so after skipping Feb 29th in 1700, they gave up and reverted the the Julian calendar in 1712 (by adding February 30th to the calendar).

that would have resulted in the two calendars remaining out of sync for 40 years. no wonder it didn't go through

This receives an extended, hilarious, discussion in Thomas Pynchon's book Mason & Dixon, in which an astronomer sits at a bar and everyone complains at him about losing their eleven days, and when they can have the days back, etc.

Pynchon is simply amazing. One day I want to be able read one of his books and understand it.

>Among the last countries in the world to accept that they were using an inaccurate calendar were the British >1752

Mmmm, Russia and much of the Orthodox world switched to Gregorian only in the 20th century

You can see the discontinuity by running:

cal 1752

in your shell!

Indeed, look closely to September:

                                   1752                               
    
           January               February                 March       
    Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa
              1  2  3  4                      1    1  2  3  4  5  6  7
     5  6  7  8  9 10 11    2  3  4  5  6  7  8    8  9 10 11 12 13 14
    12 13 14 15 16 17 18    9 10 11 12 13 14 15   15 16 17 18 19 20 21
    19 20 21 22 23 24 25   16 17 18 19 20 21 22   22 23 24 25 26 27 28
    26 27 28 29 30 31      23 24 25 26 27 28 29   29 30 31            
                                                                      
            April                   May                   June        
    Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa
              1  2  3  4                   1  2       1  2  3  4  5  6
     5  6  7  8  9 10 11    3  4  5  6  7  8  9    7  8  9 10 11 12 13
    12 13 14 15 16 17 18   10 11 12 13 14 15 16   14 15 16 17 18 19 20
    19 20 21 22 23 24 25   17 18 19 20 21 22 23   21 22 23 24 25 26 27
    26 27 28 29 30         24 25 26 27 28 29 30   28 29 30            
                           31                                         
            July                  August                September     
    Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa
              1  2  3  4                      1          1  2 14 15 16
     5  6  7  8  9 10 11    2  3  4  5  6  7  8   17 18 19 20 21 22 23
    12 13 14 15 16 17 18    9 10 11 12 13 14 15   24 25 26 27 28 29 30
    19 20 21 22 23 24 25   16 17 18 19 20 21 22                       
    26 27 28 29 30 31      23 24 25 26 27 28 29                       
                           30 31                                      
           October               November               December      
    Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa
     1  2  3  4  5  6  7             1  2  3  4                   1  2
     8  9 10 11 12 13 14    5  6  7  8  9 10 11    3  4  5  6  7  8  9
    15 16 17 18 19 20 21   12 13 14 15 16 17 18   10 11 12 13 14 15 16
    22 23 24 25 26 27 28   19 20 21 22 23 24 25   17 18 19 20 21 22 23
    29 30 31               26 27 28 29 30         24 25 26 27 28 29 30
                                                  31

> Because the people thought the government was trying to cheat them out of 11 days of their lives, there were riots in villages.

The following article goes into more detail on this point:

https://www.history.co.uk/article/the-calendar-riots-of-1752...

Edit: It sounds like it's disputed whether or not these riots actually happened.

Hah. This bit me once when a tester worked on my SQL server .NET app. As .NET supports dates before 1753 but sql server does not. Presumably because the original sybase devs didn’t want to add logic to deal with it.

First time a unit not integration test bit me as the first thing the tester did was try year 1. Unit tests for that worked perfectly, and I who had been confident at that point learnt a lesson about hubris.

The plot of an excellent Don Rosa story, "Crown of the Crusader Kings".

Although "excellent" and "Don Rosa story" are redundant :)

The history behind the Julian calendar is reminiscent of the Unix time problem(s). They were aware of the leap time issue when they designed it. Because it would take so long to accumulate enough leap days to become a burden, it just didn’t matter that much at the time of creation. 1500 years is a pretty good run!

I wonder if the java date class handles this correctly (I know it handles various weird, surprising cases)...

Faction Paradox stole those days, obviously.[1]

[1]: https://tardis.fandom.com/wiki/Eleven-Day_Empire

did the article disappear, too? When I click on the link it goes to the main page. Edit: ah, down below someone had a link: https://webcache.googleusercontent.com/search?q=cache:8TiKyG...

Archive: https://archive.fo/nGOAR

Also why 1753/01/01 is a magic number on Sql Server.

(And not because that's when Bill Gates sailed the Ocean Blue.)

The linked page is 100% ads on mobile, the article content is nowhere to be found.

There's an archived version here: https://archive.is/nGOAR

emotion note: JNRowe heavily suspires

I was going to say that cal on Linux correctly displays the weird year, then I ran "cal 9 1752" and thought I had misremembered.

Five minutes in to the rabbit hole says Debian uses bsdmainutils for cal, where on other distros you may receive util-linux's version¹. So, it is entirely dependent on an obscure choice of a maintainer whether you get the "missing" days in your output or not.

Made a thousand times stranger if, like me, you have ncal aliased to cal so that it uses your locale's week format. ncal does display the weird September for me, unless called with the -b flag for classic output. The problem is you want the -b flag if you are naïvely trying to fix the Monday should be the start of the week issue with cal.

This is my favourite quirky behaviour of at least this week, if not longer. Tonnes of sensible decisions that all interact in utterly weird ways to make very little sense without The Ultimate Shovel to dig around with.

Interestingly, ncal supports showing you where the changeover happened in various locations by providing the -p flag which shows some more data to expand on peapicker's comment.

You can even play around with the calendars in various locales with ncal by specifying the -s flag, for example "ncal -s GR 3 1924" to see peapicker's Greece example.

¹ https://github.com/karelzak/util-linux/blob/master/misc-util... - Gory handling details

> So, it is entirely dependent on an obscure choice of a maintainer whether you get the "missing" days in your output or not.

I think defaulting to removing the days in 1752 is rather Anglo-centric. That was when the British Empire adopted the Gregorian calendar, but other places adopted it earlier or later.

I can think of some other options which in my mind are all superior to using 1752 as a default:

- Work out the appropriate cutoff point based on the user's configured locale or current geographic location

- Use the original introduction of the Gregorian calendar in 1582 as the default cutoff. (This is also the correct answer for Spain, Portugal, France, Poland, Italy, and for the former members of the Spanish and Portuguese colonial empires.)

- Don't use a cutoff and just use the proleptic Gregorian calendar

- For potentially ambiguous dates – basically anything from the initial introduction of the Gregorian calendar in 1582, through to its adoption by Greece in 1923 [0] – ask the user to either choose between Julian or Gregorian, or specify a locale/country/territory for the date (from which the choice can be inferred)

[0] Turkey and Saudi Arabia adopted the Gregorian calendar after Greece did, but they don't count because they never used the Julian calendar – they switched their official calendars from Islamic to Gregorian, in 1926 and 2016 respectively. Greece was the last country to make the Julian to Gregorian switch for civil purposes

> I think defaulting to removing the days in 1752 is rather Anglo-centric.

The utility does use the locale. Since most people here probably have their locale set to en-US (or maybe en-GB/en-CA/etc.), they get the English conversion date. If you were to switch the locale to fr or es, you'd get the 1582 cutoff date. If you were to switch it to sv, you'd get Sweden's conversion date.

> The utility does use the locale.

Which utility are we talking about? As the JNRowe's comment notes, there are at least three different versions of cal in circulation: util-linux cal, bsdmainutils cal, and ncal. They don't all do the same thing.

util-linux's cal only supports three modes of operation–proleptic Gregorian, Julian, and calendar reform hardcoded to September 1752; it doesn't support any other reformation date. It uses the locale to decide whether to start the week on Monday or Sunday, but not to decide the Julian-Gregorian transition year.

BSD cal (used on macOS, Ubuntu, *BSD) only supports 1752 as a transition year and ignores the locale. BSD ncal (available on same platforms) supports other transition years and will use the configured locale to decide which one to use; however, it still falls back to 1752 as a default if locale information is not available.

To some extent that was kind of my point. Many well meaning people have tried to make better decisions at various points, but it just increases the amount of unexpected behaviour.

I suspect another better decision wouldn't really help ;)

For such niche behaviour I think I probably fall on the side of bsdmainutils' "cal -b" output. Be byte for byte compatible with old behaviour, and expect people to use something else when they need more accuracy.

Some of the behaviour you advocate for can be implemented using gcal¹, it allows you to use various dates and also specify a manual reformation date with the `--gregorian-reform=<date>` option. It doesn't offer the fuzzy sliding option though, but the manual behaviour is probably good for the people who care about this minutia.

¹ http://directory.fsf.org/project/gcal/

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