24:null 25:["$","title",null,{"children":"The International Fixed Calendar | Michaël Guitton | Observable"}] 2a:T14c0,Yearal /* use `const [Yearal]` in REPL ツ */ = (function* ( hook = "to" + (Date.prototype.toUTCString === void 0 ? "GMT" : "UTC") + "String" ) { if (!Array.prototype.toSpliced) { Array.prototype.toSpliced = function () { const duplicate = Array.from(this); this.splice.apply(duplicate, arguments); return duplicate; }; } function chunk(array, size = NaN, { callback, nudge = /* rows */ [] } = {}) { const length = array.length; const method = "function" === typeof callback ? "map" : "valueOf"; size = size || length; if (size >= length) { return array[method](callback); } const stash = []; for (let i = 0; i < length; ) { stash.push( array .slice( i, Math.min((i += size + nudge.includes(stash.length + 1)), length) ) [method](callback) ); } return stash; } function div(dividend, divisor = _00) { const remainder = dividend % divisor; return [(dividend - remainder) / divisor, remainder]; } const gregorianMonths = [ /* March */ 31, 30, 31, 30, 31, 31, 30, 31, 30, 31, /* January */ 31, 28 ]; let joint; const days = []; const _00 = 100; for (let month = 0; month < gregorianMonths.length; month++) { const monthIndex = (month + 2) % gregorianMonths.length; if (0 === monthIndex) { joint = days.length; } for (let day = 1; day <= gregorianMonths[month]; day++) { days.push(monthIndex * _00 + day); } } const daysInMonth = gregorianMonths[gregorianMonths.length - 1]; const daysPerWeek = div(daysInMonth, 4).shift(); const weeksPerMonth = div(daysInMonth, daysPerWeek).shift(); const lastMonth = div(days.length, daysInMonth).shift(); yield class Yearal { static #__bootstrap__ = (() => { Object.defineProperties(this, { months: { value: Array.from( { length: gregorianMonths.length }, (_, i) => new Date("1970-" + ("0" + ++i).slice(-2) + "-01") [hook]() .split(/,? /, 3)[2] ).toSpliced(6, 0, "Sol") }, weekDays: { value: Array.from({ length: daysPerWeek }, (_, i) => new Date( "1970-01-" + ("0" + (i + new Date(1970, 0, 1).getDay())).slice(-2) ) [hook]() .slice(0, 3) ) } }); })(); static #create = function ({ isLeapYear = false, wantArray = false, wantDays = true } = {}) { const [intercalation, nudge] = /* Leap Day */ isLeapYear ? [[days[days.length - 1] + 1], [div(lastMonth, 2).shift(), lastMonth]] : [[], [lastMonth]]; const months = chunk( days .slice( joint ) /* restore January and February as the 1st and 2nd months of the Gregorian year */ .concat(intercalation, days.slice(0, joint)), daysInMonth, { nudge } ); const year = {}; const callback = /* compute cardinal value */ (x) => div(x).pop(); const [property, args] = wantDays ? ["days", [, { callback }]] : [ "weeks", [ daysPerWeek, { callback, nudge: [weeksPerMonth] } ] ]; for (let [i, month] of months.entries()) { const count = month.filter( (x) => x < 1 + (i % (lastMonth - 1)) * _00 ).length; const crossesMonthBoundary = 0 === count ? [] : [ /* Gregorian months */ [i - 1, i], /* week number occurrence */ div(count, daysPerWeek), count ]; const endpoints = [div(month[0]), div(month[daysInMonth - 1])]; month = Object.assign( { [property]: chunk.apply(null, [month].concat(args)), endpoints }, crossesMonthBoundary.length ? { crossesMonthBoundary } : {} ); year[this.months[i]] = wantArray ? Object.values(month) : month; } return year; }; constructor( fullYear = new Date().getFullYear(), { wantArray = false, wantDays = true } = {} ) { const firstDayOftheYear = (($) => new $( /*! * whenever you provide a year argument between 0 and 99, * it is interpreted as an offset from the year 1900… * let's fix that! */ $.prototype.setUTCFullYear.call(new $(0), (fullYear = +fullYear)) ).getDay())(Date); if (isNaN(firstDayOftheYear)) { throw new RangeError("Invalid date"); } const isLeapYear = (fullYear % 4 === 0 && fullYear % 100 !== 0) || fullYear % 400 === 0; const instance = { fullYear, isLeapYear, firstDayOftheYear, has53ISOWeeks: 4 === firstDayOftheYear || (isLeapYear && 3 === firstDayOftheYear), header: Yearal.weekDays, months: Yearal.#create({ isLeapYear, wantArray, wantDays }) }; Object.freeze(Object.assign(this, instance)); } get [Symbol.toStringTag]() { return "Yearal"; } }; })()2b:[{"id":"4a76a6d24bf5982024091df027a990fa1682304e56e31938554ac73c757de8a69964f74ecdb1d75ccac27365c7808a06f95d7dfd0678b14ca591eb6b422a88e7","href":"https://static.observableusercontent.com/files/4a76a6d24bf5982024091df027a990fa1682304e56e31938554ac73c757de8a69964f74ecdb1d75ccac27365c7808a06f95d7dfd0678b14ca591eb6b422a88e7","name":"LC-DIG-ppmsca-43979.jpg","type":"image/jpeg","lastModified":1769787016343.563,"size":311679}] 28:{"id":"98c11849fc119693","slug":"the-international-fixed-calendar-a-revolutionary-concept-which-aimed-to-replace-the-gregorian-calendar","title":"The International Fixed Calendar","thumbnail":"d3f7243f3cdec47673160fddc3bca70b91fe53d3d5409807cbc9a54de4f85ae4","access_level":"public","create_time":"$D2026-01-21T11:10:12.472Z","update_time":"$D2026-03-13T06:00:07.400Z","view_time":null,"first_public_time":"$D2026-01-25T11:00:30.330Z","fork":false,"stars":0,"starred":false,"owner":{"type":"team","id":"4c1622bb5c37477f","login":"galopin","name":"Michaël Guitton","avatar_url":"https://avatars-next.observableusercontent.com/10e2fe999ac95c8686156fd07e96a686520149a4eef18a95f97795b7a7be1e29","tier":"starter_2024"},"version":66,"publish_version":null,"role":null,"authored":false,"authors":[{"type":"individual","id":"950eb34948878085","login":"galopin","name":"Michaël Guitton","avatar_url":"https://avatars-next.observableusercontent.com/b59822ff41962e9448473fadd4a11819ac725b074ad3868aabf532bade0ac00d","tier":null}],"members":[{"type":"individual","id":"950eb34948878085","login":"galopin","name":"Michaël Guitton","avatar_url":"https://avatars-next.observableusercontent.com/b59822ff41962e9448473fadd4a11819ac725b074ad3868aabf532bade0ac00d","tier":null,"role":"editor"},{"type":"team","id":"4c1622bb5c37477f","login":"galopin","name":"Michaël Guitton","avatar_url":"https://avatars-next.observableusercontent.com/10e2fe999ac95c8686156fd07e96a686520149a4eef18a95f97795b7a7be1e29","tier":"starter_2024","role":"viewer"}],"comments":[],"custom_thumbnail":false,"trashed":false,"subscribed":null,"forks":2,"collection":{"id":"10bf3880c7cb030a","slug":"date-handling","title":"Date Handling","owner":{"id":"4c1622bb5c37477f","login":"galopin","name":"Michaël Guitton"}},"type":"notebook","body":{"title":"The International Fixed Calendar","cells":[{"id":0,"value":"$${[\n md`# The International Fixed Calendar`,\n md`## A Revolutionary Concept Which Aimed to Replace the Gregorian Calendar`\n].map(($_) =>\n Object.assign($_, {\n style: \"text-wrap: balance;\"\n })\n)}","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":53,"value":"

${await FileAttachment(\"LC-DIG-ppmsca-43979.jpg\").image({ alt: 'Photograph · Commercial calendar, 1871, Buffalo, N.Y. · Sage, Sons & Co., Lith., Print’g & Mf’g Co., engraver', style: 'filter: sepia(1) hue-rotate(-125deg); max-width: 1OO%; height: auto', width: 1024, height: 820 })}

Retrieved from the Library of Congress, Prints & Photographs Division, [LC-DIG-ppmsca-43979]

","pinned":false,"hidden":false,"mode":"html","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":21,"value":"The International Fixed Calendar, a 13-month perennial calendar, was proposed around 1902 by Moses B. Cotsworth (December 3, 1859 – June 4, 1943), a British accountant, statistician, and calendar reformer.","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":20,"value":"It was financially backed by George Eastman (July 12, 1854 – March 14, 1932), an American innovator and entrepreneur who founded the Eastman Kodak Company and revolutionised photography by making it accessible to the general public.","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":19,"value":"The Gregorian calendar — with its months of varying lengths and weeks cut off unpredictably by month boundaries — imposes an avoidable burden on industry, on business practices, and upon the convenience of everyday life.","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":18,"value":"After considerable research, Cotsworth devised what is now known as the International Fixed Calendar, a solar calendar in which each of the 13 months has 28 days and four weekends. (He later named the calendar the Yearal.)","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":45,"value":"In the Cotsworth’s calendar, every month starts on a Sunday and ends on a Saturday, implying that each year also begins on a Sunday.","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":17,"value":"Thirteen months of 28 days create a precise 364-day year. A special Year Day fills the 365th day, existing outside the normal weekly cycle. This day, marked as December 29th, sits between Saturday, December 28 and Sunday, January 1, and serves as a global holiday.","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":16,"value":"The thirteenth month, Sol, is positioned between June and July.","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":15,"value":"During leap years, an extra holiday, marked as June 29th and called Leap Day, is inserted at the end of June.","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":44,"value":"$${annotate(\n `📣`,\n `Neither Leap Day nor Year Day is counted as part of any week. (In my algorithm, I am interpreting this last point somewhat flexibly.)`\n)}","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":14,"value":"This calendar also has a fascinating feature: it preserves the tradition of Friday the 13th, but now it occurs in each of the 13 months!","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":13,"value":"Cotsworth campaigned for his calendar globally, traveling extensively to promote it. His dedication to this idea spanned several decades, as he published pamphlets and promoted the calendar through various means until his later years.","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":12,"value":"

In January 1922, Moses Cotsworth packed a leather holdall, said goodbye to his family and began his campaign for a new global calendar. […] His one-man crusade to revolutionise time, modernise business and improve workers’ lives consumed his life. […] He became a close friend of George Eastman, founder of Kodak; supported by him Cotsworth travelled to over 50 countries and brought his new calendar to the verge of world-wide adoption.

— Anna J. Cook, A Man Beyond Time: Moses Cotsworth’s fight for the 13-month calendar

\n\n","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":11,"value":"Despite its innovative design, the International Fixed Calendar, which aimed to simplify timekeeping and improve business efficiency was never officially adopted by any country. Cotsworth’s efforts culminated in a conference at the League of Nations in 1931, but the proposal ultimately failed to gain widespread acceptance.","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":10,"value":"This 13-month calendar was however adopted by the Eastman Kodak Company, where it was used internally from 1928 to 1989:","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":9,"value":"

ROCHESTER, N.Y. (AP) — Starting in 1990, Eastman Kodak Co. employees will stop working 13 months a year. Kodak is abandoning the 13-month calendar developed by founder George Eastman in 1928. The change follows a task force report that concluded, ‘It’s time to harmonize the calendar.’ The change actually makes little difference to Kodak employees, except that department heads who make out 13 financial reports a year now will fill out only 12. Eastman, a busy man, probably wished he could cram more than 24 hours into a day or seven days into a week. But his 13-month calendar was intended to smooth out variations in the standard calendar, in which months can be anywhere from 28 to 31 days long and have four and sometimes five weekends.

— Associated Press, Eastman Kodak Going on Our Calendar · September 11, 1988

\n","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":33,"value":"Upon closer examination of this Kodak calendar from 1989, which can be found in various articles online, it becomes evident that it does not conform _stricto sensu_ to the Yearal calendar. This is because it doesn’t begin on January 1, the week starts on a Monday instead of a Sunday, and it contains 53 weeks rather than the standard 52. This suggests a departure from the initial proposal made in 1928.","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":32,"value":"$${annotate(\n `🦉`,\n `A Gregorian year has 53 ISO weeks if it starts on a **Thursday** or is a **leap year** that starts on a **Wednesday**. In a 400-year cycle of the Gregorian calendar, there are 71 years that have 53 ISO weeks. 1989 _does not meet any of the aforementioned criteria_.`\n)}","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":31,"value":"Regarding the 1928 sample, which is a leap year, the alignment with the Gregorian calendar is flawed since neither Leap Day nor Year Day is explicitly noted. This causes a one-day shift starting from the seventh period. Consequently, the year concludes on December 29 instead of the expected December 31.","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":30,"value":"Nevertheless, intrigued by the concept of mapping the days of the Gregorian calendar onto the Yearal calendar, I embarked on the seemingly pointless endeavor of creating an algorithm to carry out this task for any Gregorian year. From what I can tell, I believe I succeeded after a few [attempts](/d/c9e6c1b4755b5a2b) and [adjustments](/d/22fcf9a11670aa7d).","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":62,"value":"---","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":61,"value":"It took me some time to figure out that the way days of the Gregorian calendar align with the Yearal calendar is unaffected by the specific year; _only the leap year status matters_.","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":60,"value":"I can be a bit slow to catch on at times 😅","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":59,"value":"Repeating that operation every time a new instance was generated felt unnecessary. It made more sense to utilize a closure to achieve the intended result.","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":58,"value":"I put considerable thought into crafting a solution that would be compatible with both an Observable notebook and a traditional JavaScript REPL.","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":29,"value":"To be continued…","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":8,"value":"viewof verbose = Inputs.toggle({\n label: \"📆 Verbose format\",\n value: true\n})","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":50,"value":"viewof wantDays = Inputs.radio(\n new Map([\n [\"days\", true],\n [\"weeks\", false]\n ]),\n {\n value: false\n }\n)","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":7,"value":"calendar = new Yearal(void 0, { wantArray: !verbose, wantDays })","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":66,"value":"Object.prototype.toString.call(calendar)","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":27,"value":"---","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":6,"value":"$2a","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":25,"value":"match = Object.values(calendar.months)\n .map((x, i) => {\n const month = Yearal.months[i];\n const endpoints = Object.values(x).toSpliced(0, 1).shift();\n const [startsOn, endsOn] = endpoints.map((x) => $(x));\n return { month, startsOn, endsOn };\n })\n .every((x, i) => JSON.stringify(x) === JSON.stringify(data[i]))","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":24,"value":"data = d3.csvParse(\n `month,startsOn,endsOn\n 0,0/1,0/28\n 1,0/29,1/25\n 2,1/26,2/25*\n 3,2/26*,3/22*\n 4,3/23*,4/20*\n 5,4/21*,5/17*\n 6,5/18,6/15\n 7,6/16,7/12\n 8,7/13,8/9\n 9,8/10,9/7\n 10,9/8,10/4\n 11,10/5,11/2\n 12,11/3,11/30`,\n (d, _, cols) => {\n const [c1, c2, c3] = cols;\n\n const leap = new Date(calendar.fullYear, 1, 29).getDate() === 29;\n const date = (v) =>\n $(\n v\n .split(\"/\")\n .map((x, i) =>\n i ? parseInt(x, 10) - (leap && x.slice(-1) === \"*\") : +x\n )\n );\n\n return {\n [c1]: Yearal.months[+d[c1]],\n [c2]: date(d[c2]),\n [c3]: date(d[c3])\n };\n }\n)","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":23,"value":"$$ = ([monthIndex, day]) =>\n new Date(Date.UTC(calendar.fullYear, monthIndex, day))","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":22,"value":"import { annotate } from \"@galopin/misclib-routines\"","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"}],"files":"$W2b","stdlib":"1","titling":"auto"}} 29:"$28:body"