1930: Calendar Facts

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Calendar Facts
While it may seem like trivia, it (causes huge headaches for software developers / is taken advantage of by high-speed traders / triggered the 2003 Northeast Blackout / has to be corrected for by GPS satellites / is now recognized as a major cause of World War I).
Title text: While it may seem like trivia, it (causes huge headaches for software developers / is taken advantage of by high-speed traders / triggered the 2003 Northeast Blackout / has to be corrected for by GPS satellites / is now recognized as a major cause of World War I).


Ambox notice.png This explanation may be incomplete or incorrect: Created by BLACKHAT / A BOBCAT / TIME TRAVEL / BAD CODE / A VELOCIRAPTOR - Please change this comment when editing this page. Do NOT delete this tag too soon.
If you can address this issue, please edit the page! Thanks.
Randall presents what appears to be a generator of 156,000 facts, about calendars, most of which are false or have little meaning[citation needed]. The facts are seeded by a mishmash of common tidbits about the time of year.

The facts all follow the same structure: Did you know that [event] [happens at an unexpected interval] because of [interesting fact about a calendar or the Earth's movement]? Apparently [notable consequence of the fact].

Name What it is Relation to other entries
The [Fall/Spring] Equinox The time of year at which the Earth's axis is on a plane perpendicular to the line from the Earth to the Sun. Before the adoption of the Gregorian Calendar in 1582, the equinoxes fell on earlier and earlier dates as the centuries went by, due to the Julian calendar year being 365.25 days on average compared to the tropical Earth year of 365.2422 days. Pope Gregory's decision to remove the leap days on years that were multiples of 100 but not 400 corrected the average length of the calendar year to 365.2425 days. -

The formula for each generated fact goes as follows: "Did you know that [a recurring event] [occurs in an unusual manner] because of [a phenomenon or natural property]? Apparently [wild card statement]."


Ambox notice.png This transcript is incomplete. Please help editing it! Thanks.

Title: -Calendar Facts-

Shown is a branching flow chart of sorts that begins at the phrase "Did you know that", then flows through various paths to build up a sentence. (Note that the "→" arrow symbol is used below to indicate a new branch with no intermediate text from a previous branch.)

  • Did you know that:
    • the
      • Fall
      • Spring
    • the
      • Winter
      • Summer
    • Solstice
    • Olympics
    • the
      • Earliest
      • Latest
    • Sunrise
    • Sunset
    • Daylight
      • Saving
      • Savings
    • Leap
      • Day
      • Year
    • Easter
    • the
      • Harvest
      • Super
      • Blood
    • Toyota Truck Month
    • Shark Week
    • happens
      • earlier
      • later
      • at the wrong time
    every year
    • drifts out of sync with the
      • Sun
      • Moon
      • Zodiac
        • Gregorian
        • Mayan
        • Lunar
        • iPhone
      • atomic clock in Colorado
    • might
      • not happen
      • happen twice
    this year
  • because of
    • time zone legislation in
      • Indiana
      • Arizona
      • Russia
    • a decree by the pope in the 1500s
      • precession
      • libration
      • nutation
      • libation
      • eccentricity
      • obliquity
    of the
    • Moon
    • Sun
    • Earth's axis
    • equator
    • prime meridian
      • international date
      • mason-dixon
    • magnetic field reversal
    • an arbutrary decision by
      • Benjamin Franklin
      • Isaac Newton
      • FDR
  • Apparently
    • it causes a predictable increase in car accidents.
    • that's why we have leap seconds.
    • scientists are really worried.
    • it was even more extreme during the
      • Bronze Age.
      • Ice Age.
      • Cretaceous.
      • 1990s.
    • there's a proposal to fix it, but it
      • will never happen.
      • actually makes things worse.
      • is stalled in congress.
      • might be unconstitutional.
    • it's getting worse and no one knows why.

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Shouldn't it be "libration" not "libation"? Pretty sure drinking has nothing to do with it. Also pretty sure this is a mistake and not a clever alteration. 16:41, 18 December 2017 (UTC)

No, it's a clever alteration because "libration" is listed right above it. --Videblu (talk) 16:45, 18 December 2017 (UTC)
That's just a mistake - he meant to write 'vibration' 16:48, 18 December 2017 (UTC)
'Vibration' wouldn't make any sense, 'libation' is at least humorous, I vote it was no mistake. 18:00, 18 December 2017 (UTC)
You're right - I don't know what I could have been thinking... 08:49, 19 December 2017 (UTC)

I formatted the transcript into a bullet tree since I thought it was the closest equivalent you can get in plain text to the branching flowchart deal in the comic. I'm open to alternative suggestions. The biggest problem I encountered, and one I'd like to see resolved, is what to do in the case where two branching sections butt up against each other, e.g. winter/summer and solstice/Olympics. I used an arrow symbol ("→") on an in-between line just to separate the set of bullets, but if someone wants to change that, I'm up for it. Kenbellows (talk) 18:04, 18 December 2017 (UTC)

I find the bullet tree legible for the last few long lines, but it's hard to follow a single path. I was thinking of using (option 1|option 2) syntax, but that would probably look messy too. 18:10, 18 December 2017 (UTC)
I think indenting when lines diverge and un-indenting when they converge would make it look nice and be easy to follow. I'm willing to do the work if others agree. 23:58, 18 December 2017 (UTC)
Could you do it? I don't see what it looks like. Is it similar to this? 06:16, 19 December 2017 (UTC)

Random error noticed - the line connecting "International Date" and "Mason-Dixon" to "Line" is drawn in the wrong color. 18:57, 18 December 2017 (UTC)

Isn't the point with this comic that there is at least one valid path for every included element? I don't think Randall intended it to be a factorial combination because as the explanation suggests, most would be wrong/absurd/silly. But why not instead try to find some invalid element when it can be included in any possible path from end to end? Toyota Truck Month or Shark Week might not happen next year, who knows? Can anyone find any element that has no valid path at all? If not, then maybe the main explanation should be updated to fit the model recommended here.Lunar7 (talk) 20:05, 18 December 2017 (UTC)

I'm not sure there's any 'fact' that could be constructed that 'scientists are really worried' about. Unless it's something to do with Shark Week. Although having said that, it doesn't actually say that they're worried 'about it', so I guess you could append this to any otherwise true fact and still have something true, albeit non sequitous. 08:53, 19 December 2017 (UTC)

I'm pretty sure the whole point of this comic was to be a "screw you" to the Explain XKCD crew. Way to roll with the punches. (talk) (please sign your comments with ~~~~)


PIBWEB online generator of Calendar 'facts' using this formula.

http://calendarfact.com/ (https://github.com/mstratman/calendarfact)


Not sure who's responsible for this, but there seem to be a few errors. "Might (not happen/happen twice) this year" is missing "this year", and "the (harvest/super/blood) moon" is similarly missing "moon". Also, I see a part "happens at the same time every year" that I don't see in the comic. Are there any other additions; and is there a way to find them other than keep refreshing? -- Angel 18:40, 18 December 2017 (UTC)
Checked the source; looks like "at the same time" replaces "at the wrong time". Also, some of the options are missing a "." between the main tree and the title text or at the end of the sentence. (And for some reason every time I go to edit this talk page, the wiki logs me out) -- 18:48, 18 December 2017 (UTC)
The source is on github - you can add pull requests to fix errors (I'll take care of the aforementioned errors).

Here's mine.


Here's one I wrote on jsFiddle. Glad I'm not the only one who read this and immediately thought, "I must code this!" 21:29, 18 December 2017 (UTC)


Here's a GraphML gist that I knocked up:


The only change I made was to "precession", "libration", etc by adding the word "the" in front because it reads better. At least to my British English sensibilities. YLMV.

I tuned it into a twitter bot: http://twitter.com/xkcd_cal_facts. It’s built using Tracery and cheapbotsdonequick.com


I made one too! https://jsfiddle.net/kr661rhy/

Here's my python implementation (it ain't pretty, but then I'm not very good at python yet, either):


And my Crystal implementation:


As there are many generators isn't better to remove links to generators from the comic explanation and add a link to this section?

Here is my implementation in Haskell:

https://github.com/mwuttke97/xkcd1930 19:57, 20 December 2017 (UTC)

I made a Python command and function;

YehudaDe (talk) 08:43, 21 December 2017 (UTC)

I wrote a command line tool in node.js. My code's pretty concise because it doesn't hard code all possible options for each "piece" but uses the "(choice|choice|choice)" syntax.

I created a human-readable file format to represent structures like the one in the comic, then wrote a C program to parse those files, so now you can write your own calendar facts.


I don't think this is the correct definition for equinox, the plane comprising the Earth orbit around the Sun is never perpendicular to the Earth's axis. During the equinox the sun rays arrive to the Earth perpendicular to the equator line, this would be better. 22:10, 18 December 2017 (UTC)CBM

I agree with the comment above; the Earth's axis is always tilted 23 degrees from the plane of the orbit. There are times the North pole is tilted toward the Sun and times it is tilted away from the Sun. Twice a year (at the equinoxes) the tilt is perpendicular to the Sun. 22:47, 18 December 2017 (UTC)
I've edited the descriptions - do they look better now? 00:32, 19 December 2017 (UTC)
Daylight Saving Time

Twice the description references locations that don't follow the common DST plan as 'other than the natural latitude would suggest'. The longitude would suggest a time zone, not the latitude. 22:47, 18 December 2017 (UTC)

Arbitrary decision by Benjamin Franklin

The electric charge on an electron is conventionally described as being negative. I was always taught that this was because of a more or less arbitrary decision made by Franklin. I suspect Mr Munroe is humorously conflating this with Franklin's connection to Daylight Saving Time.

Favorite combinations

My personal favorite: “Did you know that Toyota Truck Month happens at the wrong time every year because of a decree by the pope in the 1500s? Apparently it’s getting worse and no one knows why. While it may seem like trivia, it is now recognized as a major cause of World War 1. PotatoGod (talk) 02:06, 19 December 2017 (UTC)

Got this from the link to the fact generator, and I like that too, maybe because it is close to the one above, which I first saw now:

Calendar Facts by xkcd
Did you know that Shark Week drifts out of sync with the sun because of a decree by the pope in the 1500s?
Apparently it's getting worse and no one knows why.
While it may seem like trivia, it triggered the 2003 Northeast Blackout.

Damn sharks and pope decree. --Kynde (talk) 10:08, 19 December 2017 (UTC)

"Did you know that Shark Week might happen twice this year because of..." Sold. Don't care about the rest. 23:28, 20 December 2017 (UTC)

Is no one going to mention that "Shark Week" sometimes is used as slang to refer to menstruation? That's what I thought of the moment I saw it, and since cycles are roughly every 28 days but can change length slowly to re-synchronize (with others or for various reasons) that might be another valid interpretation. 20:14, 31 December 2017 (UTC)Rowan

What's incomplete in this explanation? Seems pretty exhaustive to me. Can't we remove the incomplete tag? Zetfr 15:09, 2 May 2018 (UTC)

The explanation says the comic generates facts. But as most of them are false it should refer to them as factoids. 11:19, 18 February 2020 (UTC)

I don't see it... it clearly says it "appears to be a generator of 156,000 facts [...], about calendars, most of which are false or have little meaning" with the word appears and the statement following right after, that most are false.--Lupo (talk) 13:03, 18 February 2020 (UTC)