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Dates That Don't Exist (2015)

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Re: Dates That Don't Exist (2015)

#61

Post by ButlerianJihad »

autarch wrote: post #41
dinkelberg wrote: post #38

Earlier quoted context omitted.

Who else uses the proleptic Gregorian calendar other than programmers of datetime libraries?

Who writes computer programs that deal with pre-1582 _dates_ at all? In science-related code, I can image a case for calculating things like seconds elapsed across a very long time period. But in that case you're not really dealing with dates. Instead, you want something like the Unix epoch, but probably with an earlier epoch start. There may be some very niche cases for pre-1582 dates in code that I'm not thinking o…

Astronomy

Re: Dates That Don't Exist (2015)

#62

Post by netsharc »

maxlybbert wrote: post #33

This is an interesting detail to learn about history. However, like the article mentions near the end, the Gregorian calendar was adopted at different times in different countries. The Anglican Church didn’t trust the Catholics, so Great Britain adopted the Gregorian calendar in 1752 ( https://en.wikipedia.org/wiki/Calendar_(New_Style)_Act_1750 ). And they did their best to hide the fact that they were adopting a Cat…

1752 is before the invention of timezones, but that adds another curiousity about "what date did X happen?". On the calendar of Country A it could've been October 31, 1752, and on the calendar of Country B it would've been October 21...

Re: Dates That Don't Exist (2015)

#63

Post by philjohn »

autarch wrote: post #41
dinkelberg wrote: post #38

Earlier quoted context omitted.

Who else uses the proleptic Gregorian calendar other than programmers of datetime libraries?

Who writes computer programs that deal with pre-1582 _dates_ at all? In science-related code, I can image a case for calculating things like seconds elapsed across a very long time period. But in that case you're not really dealing with dates. Instead, you want something like the Unix epoch, but probably with an earlier epoch start. There may be some very niche cases for pre-1582 dates in code that I'm not thinking o…

Library and Archival management systems

Lots of written work pre 1582 that needs to be accurately catalogued.

Source: I used to work on one of the first computerised library management software systems, and plenty of our academic customers had manuscripts dating back that far.

Re: Dates That Don't Exist (2015)

#64

Post by ks2048 »

russdill wrote: post #25

This is clearly the wrong way to think about it. Dates forward and backward from this flag date exist in both calendars and it's straightforward to convert between them. Such a flag day didn't involve removing days from one calendar or the other, it switched between them.

I would think of it as Calendar A uses Calandar B until time point T and then uses Calendar C. These dates exist in Calendars B and C, but do not exist in Calendar A.

Re: Dates That Don't Exist (2015)

#65

Post by ks2048 »

autarch wrote: post #41
dinkelberg wrote: post #38

Earlier quoted context omitted.

Who else uses the proleptic Gregorian calendar other than programmers of datetime libraries?

Who writes computer programs that deal with pre-1582 _dates_ at all? In science-related code, I can image a case for calculating things like seconds elapsed across a very long time period. But in that case you're not really dealing with dates. Instead, you want something like the Unix epoch, but probably with an earlier epoch start. There may be some very niche cases for pre-1582 dates in code that I'm not thinking o…

I've been writing some programs to deal with the Maya Calendars, where it is an issue.

On some level, it doesn't matter if an inscription corresponds to "August 31, 83 CE" or "September 2, 83 CE" (a date potentially inscribed at the site Takalik Abaj in Proleptic Gregorian or Julian), but it's nice to try to get the details correct. And if you want to correlate with other events in history (especially if you can find astronomical event data from Europe), you need to be at least consistent.

Plus, it's just fun to think about these events from long ago in terms (dates) we understand.

Re: Dates That Don't Exist (2015)

#66

Post by madcaptenor »

zanecodes wrote: post #58

Dealing with dates becomes much simpler conceptually when you realize that you are actually dealing with two different ideas masquerading as one: dates, and the actual instants in time which they name. Instants in time can only be unambiguously referenced by measuring some fixed unit of time intervals from some commonly agreed upon event (e.g. seconds since the Unix Epoch). Dates are a mapping from human-readable lab…

I get what you're saying, but if the government repealed the Gregorian calendar (and went back to Julian) that wouldn't change the day of the week. The day of the week is historically independent of the day of the month. Catholics and Protestants agreed on this in the calendar change. The original papal bull that set up the Gregorian calendar has Thursday 1582-10-04 followed by Friday 1582-10-15; Great Britain and colonies (if we're taking the US perspective) followed Wednesday 1752-09-02 with Thursday 1752-09-14.

Re: Dates That Don't Exist (2015)

#67

Post by da_chicken »

Asraelite wrote: post #51
da_chicken wrote: post #31

Earlier quoted context omitted.

It's not a wrong way to think about it. There are some use cases for proleptic calendars, but there are just as many where it's completely inappropriate. If you ever need to compare what day you think it is with what day someone in the past thought it was, then yes those dates don't exist in any real sense. I wouldn't say it's it's straightforward to convert between them, either. The Gregorian calendar was first adop…

I would say it's almost never appropriate unless you're directly quoting source texts. If you are talking about a historical event from Egypt in 500 BCE, you would say "this happened in 500 BCE", not "this happened in year 26 of the 27th dynasty". The distinction is important in the context of doing historical research, but it is no more appropriate to write dates in secondary sources using the Julian calendar than i…

Yeah, but how often are we talking about exactly specific dates without referring to specific historical texts?

The Magna Carta was sealed on June 15, 1215 for the Julian calendar. But if you want the actual anniversary, it was sealed on June 22, 1215 using the proleptic Gregorian calendar. Do you want to know the date people remember, ir the date of the true anniversary?

The coronation of Henry VIII is listed almost everywhere you look as June 24, 1509. Except that's also Julian. The date of the Gregorian calendar is July 4, 1509.

We don't remember the proleptic dates. We remember the dates that were then in use.

And if you say you're just always going to use the contemporary recorded date, that's fine. Until you get to dates like February 29, 1700. What do you put in your system then?

Re: Dates That Don't Exist (2015)

#68

Post by _kst_ »

tshaddox wrote: post #49
maxlybbert wrote: post #33

This is an interesting detail to learn about history. However, like the article mentions near the end, the Gregorian calendar was adopted at different times in different countries. The Anglican Church didn’t trust the Catholics, so Great Britain adopted the Gregorian calendar in 1752 ( https://en.wikipedia.org/wiki/Calendar_(New_Style)_Act_1750 ). And they did their best to hide the fact that they were adopting a Cat…

The British (including the American colonies) also did an arguably even more confusing calendar change in 1752, by switching the start of the new year from March 25 to January 1.

Does that really mean that the day after 24 March 1750 was 25 March 1751?

Re: Dates That Don't Exist (2015)

#69

Post by zanecodes »

madcaptenor wrote: post #66
zanecodes wrote: post #58

Dealing with dates becomes much simpler conceptually when you realize that you are actually dealing with two different ideas masquerading as one: dates, and the actual instants in time which they name. Instants in time can only be unambiguously referenced by measuring some fixed unit of time intervals from some commonly agreed upon event (e.g. seconds since the Unix Epoch). Dates are a mapping from human-readable lab…

I get what you're saying, but if the government repealed the Gregorian calendar (and went back to Julian) that wouldn't change the day of the week. The day of the week is historically independent of the day of the month. Catholics and Protestants agreed on this in the calendar change. The original papal bull that set up the Gregorian calendar has Thursday 1582-10-04 followed by Friday 1582-10-15; Great Britain and co…

Interesting, I didn't know that! I suppose I could edit my post accordingly, maybe a better example would be "the pharmacy won't let me get a refill until the date written on my prescription: Wednesday, August 12th 2026"? I think the point gets across regardless.

Re: Dates That Don't Exist (2015)

#70

Post by maxlybbert »

_kst_ wrote: post #68
tshaddox wrote: post #49

Earlier quoted context omitted.

The British (including the American colonies) also did an arguably even more confusing calendar change in 1752, by switching the start of the new year from March 25 to January 1.

Does that really mean that the day after 24 March 1750 was 25 March 1751?

I think so.

Look at https://en.wikipedia.org/wiki/New_Year#Annunciation_Style :

“Despite the unification of the Scottish and English royal crowns with the accession of King James VI and I in 1603, and even the union of the kingdoms themselves in 1707, England continued to use Annunciation Style while Scotland used Modern Style. This led to the act being recorded at the time in England as 6 March 1706 (rather than 1707), because in England (unlike Scotland) it fell before the new year began (on 25 March).”

It apparently caused trouble for travelers (from the New Style Calendar Act https://en.wikisource.org/wiki/Calendar_(New_Style)_Act_1750 ):

“WHEREAS the legal Supputation of the Year of our Lord in that Part of Great Britain called England, according to which the Year beginneth on the 25th Day of March, hath been found by Experience to be attended with divers Inconveniencies, not only as it differs from the Usage of neighbouring Nations, but also from the legal Method of Computation in that Part of Great Britain called Scotlond, and from the common Usage throughout the whole Kingdom, and thereby frequent Mistakes are occasioned in the Dates of Deeds, and other Writings, and Disputes arise therefrom.”

Although, I think “common usage” in that statement implies that it was common to just do what other countries did, except when filling out legal documents.

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