71–80 of 90 posts
Earlier quoted context omitted.
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
If not I'd argue the system should disallow dates before the switchover.
Ok now do date math, does the day-of-month accurately jump over the non-existent numbers?
I maintain an Elixir library (Calendrical) that does this. England, for example, is just three segments spliced onto a Julian base:
defmodule England do
use Calendrical.Composite,
calendars: [
~D[1155-03-25 Calendrical.Julian.March25], # year starts on Lady Day
~D[1751-03-25 Calendrical.Julian.Jan1], # New Year moved to Jan 1
~D[1752-09-14 Calendrical.Gregorian] # the 11-day jump
],
base_calendar: Calendrical.Julian
end
England.days_in_month(1752, 9) #=> 19
England.valid_date?(1752, 9, 3) #=> false
Date.shift(~D[1752-09-02 England], day: 1) #=> ~D[1752-09-14 England]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…
There seems to be disagreement about the year. Two systems I checked assume 1752, not 1582. (OpenBSD) $ man cal [...] The Gregorian Reformation is assumed to have occurred in 1752 after the 2nd of September. By this time, most countries had recognized the Reformation (although a few did not recognize it until the early 1900s). Eleven days following that date were eliminated by the Reformation, so the calendar for tha…
It depends on the country. 1582 is Catholic Europe 1700 or 1701 is Protestant Europe 1752 is Great Britain and its colonies which include USA 1918 is Russia 1923 Greece https://en.wikipedia.org/wiki/Adoption_of_the_Gregorian_cale...
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?
Also, there is an unofficial "Old New Year" eve on 1/13, which people recognize as the "old style" New Year eve, even though more than 100 years have passed since the calendar change.
Earlier quoted context omitted.
Who else uses the proleptic Gregorian calendar other than programmers of datetime libraries?
It's typically not used in modern historical writing when referring to events located in areas that used the Julian calendar at that time. But it is typically used when referring to events located in areas with no calendar system familiar to modern readers, most notably the Maya calendar. Maya Long Count dates are typically converted to the proleptic Gregorian calendar. Also, many modern historical writings will disp…
To follow up on this, George Washington is a great example. He was born about 20 years before the British calendar changed from Julian to Gregorian and changed the new year from beginning on March 25 to January 1.
The vast majority of modern sources will cite Washington's birthday as February 22, 1732, which is actually the proleptic Gregorian calendar (called "New Style"). George Washington himself would have said that his birthday was February 11, 1731, at least until the British calendar changed in 1752 (at which point he probably would have still used the "Old Style" since it would have been clear from context).
Using the proleptic Gregorian calendar for historical dates is only a problem if you want to compute the day of the week (which those missing days will throw off prior to the adoption of the Gregorian calendar in the relevant country) or the number of days between two historical dates (if the two dates span the date when the Gregorian calendar was adopted). And, frankly, there are other problems to deal with beyond c…
Dates are messy.
This article presents a grossly simplified version of events. The truth is that only some catholic countries switched in 1582. Britain and its colonies switched in 1752. Prussia switched in 1610. And so on.
Hadn't Britain established the C of E permanently by 1570, so it wasn't part of the Catholic world any more?