7 ms·

From Julian to Gregorian Calendar

56 points by techolic 9y ago

martimoose 9y ago
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 9y ago
  ...and then there's Julian Day (JD). https://en.wikipedia.org/wiki/Julian_day https://en.wikipedia.org/wiki/Julian_day
  - martimoose 9y ago
    ... and then there's JD combined with Delta T https://en.wikipedia.org/wiki/%CE%94T https://en.wikipedia.org/wiki/%CE%94T
nradov 9y ago
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 9y ago
  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 9y ago
    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 :)
    - greglindahl 9y ago
      It's amusing that Twelfth Night is so little known, despite the play, the "12 days of Christmas", and so on.
      - madcaptenor 9y ago
        I suspect if you asked most people when the 12 days of Christmas are, they'd say they were December 14-25 (or maybe even 13-24). After all, that's when you buy the presents!
    - Mikeb85 9y ago
      That holiday is Epiphany, which is a separate holiday (and I believe actually falls on the 6th of January on the Gregorian calendar).
    - Grustaf 9y ago
      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.
      - icebraining 9y ago
        Yes, it's a coincidence, that's why I find it curious :)
      - goptimize 9y ago
        Christmas in Russia is celebrated on 7 January
abruzzi 9y ago
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 9y ago
  Is this a spoiler for the novel?
  - twic 9y ago
    It's not the kind of novel where knowing something like that will make a difference.
    - abruzzi 9y ago
      Yeah, there are hundreds of little esoteric facts like that contribute to the conspiracy theory. So no spoilers.
mikeash 9y ago
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.
- deleted 9y ago
  [deleted]
ceautery 9y ago
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:xrRtualQoz8J:https://curtisautery.appspot.com/5779342353235968 https://webcache.googleusercontent.com/search?q=cache:xrRtua... (edit ...and Google cache is being ornery right now.)
acomjean 9y ago
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 9y ago
  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...)
Avernar 9y ago
"Switch Took More Than 300 Years" I sure hope the complete switchover from IPv4 to IPv6 also doesn't end up taking that long.

56 points by techolic 9y ago

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 9y ago
...and then there's Julian Day (JD). https://en.wikipedia.org/wiki/Julian_day https://en.wikipedia.org/wiki/Julian_day
- martimoose 9y ago
  ... and then there's JD combined with Delta T https://en.wikipedia.org/wiki/%CE%94T https://en.wikipedia.org/wiki/%CE%94T

nradov 9y ago

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 9y ago
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 9y ago
  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 :)
  - greglindahl 9y ago
    It's amusing that Twelfth Night is so little known, despite the play, the "12 days of Christmas", and so on.
    - madcaptenor 9y ago
      I suspect if you asked most people when the 12 days of Christmas are, they'd say they were December 14-25 (or maybe even 13-24). After all, that's when you buy the presents!
  - Mikeb85 9y ago
    That holiday is Epiphany, which is a separate holiday (and I believe actually falls on the 6th of January on the Gregorian calendar).
  - Grustaf 9y ago
    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.
    - icebraining 9y ago
      Yes, it's a coincidence, that's why I find it curious :)
    - goptimize 9y ago
      Christmas in Russia is celebrated on 7 January

abruzzi 9y ago

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 9y ago
Is this a spoiler for the novel?
- twic 9y ago
  It's not the kind of novel where knowing something like that will make a difference.
  - abruzzi 9y ago
    Yeah, there are hundreds of little esoteric facts like that contribute to the conspiracy theory. So no spoilers.

mikeash 9y ago

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.

deleted 9y ago
[deleted]

ceautery 9y ago

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:xrRtualQoz8J:https://curtisautery.appspot.com/5779342353235968 https://webcache.googleusercontent.com/search?q=cache:xrRtua... (edit ...and Google cache is being ornery right now.)

acomjean 9y ago

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 9y ago
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...)

Avernar 9y ago

"Switch Took More Than 300 Years" I sure hope the complete switchover from IPv4 to IPv6 also doesn't end up taking that long.