Data update

Task/French-Republican-calendar/JavaScript/french-republican-calendar.js

@@ -0,0 +1,130 @@
+class FrenchRCDate {
+    constructor(year, month, day) {
+        this.year = year;
+        this.month = month;
+        this.day = day;
+    }
+
+    static INTRODUCTION_DATE = new Date(Date.UTC(1792, 8, 22)); // Months are zero-indexed in JS
+    static TERMINATION_DATE = new Date(Date.UTC(1805, 11, 31));
+
+    static MONTHS = [
+        "Vendémiaire", "Brumaire", "Frimaire", "Nivôse", "Pluviôse", "Ventôse",
+        "Germinal", "Floréal", "Prairial", "Messidor", "Thermidor", "Fructidor"
+    ];
+
+    static SANSCULOTTIDES = [
+        "Fête de la vertu", "Fête du génie", "Fête du travail",
+        "Fête de l'opinion", "Fête des récompenses", "Fête de la Révolution"
+    ];
+
+    toGregorianDate() {
+        const days = (this.year - 1) * 365 + FrenchRCDate.additionalDaysForYear(this.year) +
+                     (this.month - 1) * 30 + this.day - 1;
+
+        const gregorian = new Date(FrenchRCDate.INTRODUCTION_DATE);
+        gregorian.setUTCDate(gregorian.getUTCDate() + days);
+        return gregorian;
+    }
+
+    toString() {
+        if (this.month < 13) {
+            return `${this.day} ${FrenchRCDate.MONTHS[this.month - 1]} ${this.year}`;
+        } else {
+            return `${FrenchRCDate.SANSCULOTTIDES[this.day - 1]} ${this.year}`;
+        }
+    }
+
+    static additionalDaysForYear(year) {
+        return year > 11 ? 3 : year > 7 ? 2 : year > 3 ? 1 : 0;
+    }
+
+    static toFrenchRCDate(gregorianDate) {
+        const daysAfter = Math.floor((gregorianDate - FrenchRCDate.INTRODUCTION_DATE) / (1000 * 60 * 60 * 24));
+        const daysBefore = Math.floor((FrenchRCDate.TERMINATION_DATE - gregorianDate) / (1000 * 60 * 60 * 24));
+
+        if (daysAfter < 0 || daysBefore < 0) {
+            throw new Error("French Republican Calendar date out of range.");
+        }
+
+        let year = Math.floor((daysAfter + 366) / 365);
+        let days = (daysAfter + 366) % 365 - FrenchRCDate.additionalDaysForYear(year);
+
+        if (days < 1) {
+            year -= 1;
+            days += 366;
+        }
+
+        if (days < 361) {
+            const month = Math.floor(days / 30) + 1;
+            const day = days % 30 || 30;
+            return new FrenchRCDate(year, month, day);
+        } else {
+            const day = days - 360;
+            return new FrenchRCDate(year, 13, day);
+        }
+    }
+
+    static parse(frenchRCDateString) {
+        const parts = frenchRCDateString.trim().split(/\s+/);
+        if (parts.length === 3) {
+            const [dayStr, monthStr, yearStr] = parts;
+            const year = parseInt(yearStr, 10);
+            const month = FrenchRCDate.MONTHS.indexOf(monthStr) + 1;
+            const day = parseInt(dayStr, 10);
+            return new FrenchRCDate(year, month, day);
+        } else {
+            const yearStr = parts[parts.length - 1];
+            const year = parseInt(yearStr, 10);
+            const sansculottideName = parts.slice(0, -1).join(" ");
+            const day = FrenchRCDate.SANSCULOTTIDES.indexOf(sansculottideName) + 1;
+            return new FrenchRCDate(year, 13, day);
+        }
+    }
+}
+
+// Helper to format dates like "d MMMM yyyy"
+function formatDate(date) {
+    const months = [
+        "January", "February", "March", "April", "May", "June",
+        "July", "August", "September", "October", "November", "December"
+    ];
+    const day = date.getUTCDate();
+    const month = months[date.getUTCMonth()];
+    const year = date.getUTCFullYear();
+    return `${day} ${month} ${year}`;
+}
+
+// Main logic
+const gregorianStrings = [
+    "22 September 1792",
+    "20 May 1795",
+    "15 July 1799",
+    "23 September 1803",
+    "31 December 1805"
+];
+
+const frenchRCStrings = [];
+
+for (const gregorianString of gregorianStrings) {
+    // Parse into JS Date object
+    const [day, month, year] = gregorianString.split(" ");
+    const monthIndex = [
+        "January", "February", "March", "April", "May", "June",
+        "July", "August", "September", "October", "November", "December"
+    ].indexOf(month);
+    const gregorianDate = new Date(Date.UTC(parseInt(year), monthIndex, parseInt(day)));
+
+    const frenchRCDate = FrenchRCDate.toFrenchRCDate(gregorianDate);
+    const frenchRCString = frenchRCDate.toString();
+    frenchRCStrings.push(frenchRCString);
+    console.log(`${gregorianString} => ${frenchRCString}`);
+}
+
+console.log();
+
+for (const frenchRCString of frenchRCStrings) {
+    const frenchRCDate = FrenchRCDate.parse(frenchRCString);
+    const gregorianDate = frenchRCDate.toGregorianDate();
+    console.log(`${frenchRCString} => ${formatDate(gregorianDate)}`);
+}