
From Julian to Gregorian Calendar - techolic
https://www.timeanddate.com/calendar/julian-gregorian-switch.html
======
mikeash
I was glad to see that this included my favorite calendrical fact: the
existence of February 30th, in just one year in Sweden.

It misses another good one, which is what happened in Alaska. Alaska's
transition from Julian to Gregorian happened when ownership of the territory
transferred from Russia to the United States. This also involved moving Alaska
to the other side of the International Date Line (or more correctly, moving
the Date Line to the other side of Alaska). The net effect was that, in
Alaska, Friday, October 6th, 1867 was followed by Friday, October 18th.

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abruzzi
If you ever read Umberto Eco's novel "Foucault's Pendulum" this is a key plot
point. Specifically some shadowy "conspiracy" group was set to meet, but the
meeting never happened because some countries had revised their calendar and
some hadn't so they missed each other. Its a great novel about secret
societies, conspiracy theories, and peoples willingness to believe them.

~~~
jonathanpoulter
Is this a spoiler for the novel?

~~~
twic
It's not the kind of novel where knowing something like that will make a
difference.

~~~
abruzzi
Yeah, there are hundreds of little esoteric facts like that contribute to the
conspiracy theory. So no spoilers.

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martimoose
Fun fact: astronomers (and Nasa) use the Julian calendar for events (for
example eclipses) before october 1582. You'd think they use UT, but they
don't, so you can match historical dates with celestial events. Also worth
noting, astronomical year numbering has a year 0, whereas BC/AD system does
not, so that year 0 is 1 BC.

You have to make time corrections when you program something related to
astronomy. In most things we program, UT is an absolute on which we can rely,
but when we go very far away in the past it's not that clear anymore.

~~~
thriftwy
...and then there's Julian Day (JD).

[https://en.wikipedia.org/wiki/Julian_day](https://en.wikipedia.org/wiki/Julian_day)

~~~
martimoose
... and then there's JD combined with Delta T
[https://en.wikipedia.org/wiki/%CE%94T](https://en.wikipedia.org/wiki/%CE%94T)

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acomjean
Unix seems to handle it well:

$cal 9 1752

    
    
        September 1752
     Su Mo Tu We Th Fr Sa
            1  2 14 15 16
     17 18 19 20 21 22 23
     24 25 26 27 28 29 30
    

there is a Bug on the man page, which has more to do with "what country are we
in" BUGS The assignment of Julian--Gregorian switching dates to country codes
is historically naive for many countries.

~~~
madcaptenor
ncal allows me to specify the country, so even though I'm in the US I can get
the following:

    
    
      $ ncal -sES 10 1582
          October 1582
      Mo  1 18 25
      Tu  2 19 26
      We  3 20 27
      Th  4 21 28
      Fr 15 22 29
      Sa 16 23 30
      Su 17 24 31
    

(Alas, ncal -sSW 2 1712 doesn't get February of 1712 right in Sweden...)

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Avernar
"Switch Took More Than 300 Years"

I sure hope the complete switchover from IPv4 to IPv6 also doesn't end up
taking that long.

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nradov
The Serbian Orthodox Church _still_ hasn't switched from the Julian calendar.
So now their religious holidays like Christmas are a couple weeks off from the
rest of the world and will continue diverging.

~~~
madcaptenor
Isn't that all Orthodox churches, not just the Serbian?

My wife's a bit of a Russophile. So in years where we forgot to do the holiday
shopping, we exchange gifts on Russian Christmas (i. e. January 7, Gregorian).
Or, if we're _really_ forgetful, Russian New Year.

~~~
icebraining
Curiously, January 7 is also when many Spanish families exchange gifts,
supposedly as a celebration of the arrival of the Magi/Three Wise Kings (who
brought gifts to Jesus).

This is much to the annoyance of Spanish kids with foreign friends :)

~~~
Grustaf
Yes, but that is a coincidence. Russians celebrate Christmas on December 25th
like everyone else (except some norther Europeans, we celebrate on the eve),
it's just that their view of when it is December 25th differs.

~~~
goptimize
Christmas in Russia is celebrated on 7 January

~~~
Grustaf
My point was that no, the holidays are celebrated on the same dates throughout
the Christian world, but depending on which calendar you use those dates fall
on different days. Today for example it's August 10th in many Orthodox
churches, while most others would say it's the 23rd.

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ceautery
That's cool, I hadn't ever heard about Sweden's double-leap years.

I did some research on calendars a while back, and notably, the conversion to
Gregorian had a lot of religious overtones. Here's what I wrote about it:

[https://webcache.googleusercontent.com/search?q=cache:xrRtua...](https://webcache.googleusercontent.com/search?q=cache:xrRtualQoz8J:https://curtisautery.appspot.com/5779342353235968)

(edit ...and Google cache is being ornery right now.)

