Fix Chanukah URL for previous year when final days are in January

Author: mjradwin

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@hebcal/core",
-  "version": "5.8.9",
+  "version": "5.8.10",
   "author": "Michael J. Radwin (https://github.com/mjradwin)",
   "contributors": [
     "Eyal Schachter (https://github.com/Scimonster)",

src/HolidayEvent.ts

@@ -112,7 +112,7 @@ export class HolidayEvent extends Event {
 
 /**
  * Because Asara B'Tevet often occurs twice in the same Gregorian year,
- * we subclass HolidayEvent to override the `url()` method.
+ * we subclass HolidayEvent to generate the correct URL.
  */
 export class AsaraBTevetEvent extends HolidayEvent {
   urlDateSuffix(): string {
@@ -121,6 +121,21 @@ export class AsaraBTevetEvent extends HolidayEvent {
   }
 }
 
+/**
+ * Because Chanukah sometimes starts in December and ends in January,
+ * we subclass HolidayEvent to generate the correct URL.
+ */
+export class ChanukahEvent extends HolidayEvent {
+  urlDateSuffix(): string {
+    const dt = this.getDate().greg();
+    let year = dt.getFullYear();
+    if (dt.getMonth() === 0) {
+      year--;
+    }
+    return String(year);
+  }
+}
+
 /** Represents Rosh Hashana, the Jewish New Year */
 export class RoshHashanaEvent extends HolidayEvent {
   private readonly hyear: number;

src/holidays.ts

@@ -31,6 +31,7 @@ import {
 import {YomKippurKatanEvent} from './YomKippurKatanEvent';
 import {
   HolidayEvent,
+  ChanukahEvent,
   AsaraBTevetEvent,
   RoshHashanaEvent,
   RoshChodeshEvent,
@@ -190,7 +191,7 @@ export function getHolidaysForYear_(year: number): HolidayYearMap {
   for (let candles = 2; candles <= 8; candles++) {
     const hd = new HDate(23 + candles, KISLEV, year);
     add(
-      new HolidayEvent(
+      new ChanukahEvent(
         hd,
         `Chanukah: ${candles} Candles`,
         MINOR_HOLIDAY | CHANUKAH_CANDLES,
@@ -202,7 +203,7 @@ export function getHolidaysForYear_(year: number): HolidayYearMap {
     );
   }
   add(
-    new HolidayEvent(
+    new ChanukahEvent(
       new HDate(32, KISLEV, year),
       hdesc.CHANUKAH_8TH_DAY,
       MINOR_HOLIDAY,

test/holidays.spec.js

@@ -154,6 +154,23 @@ test('asara-btevet-url', () => {
   expect(urls).toEqual(expected);
 });
 
+test('chanukah-url', () => {
+  const events = HebrewCalendar.calendar({
+    start: new Date(2024, 11, 30),
+    end: new Date(2025, 0, 2),
+  });
+  const urls = events
+      .filter((ev) => ev.basename() === 'Chanukah')
+      .map((ev) => ev.url());
+  const expected = [
+    'https://www.hebcal.com/holidays/chanukah-2024',
+    'https://www.hebcal.com/holidays/chanukah-2024',
+    'https://www.hebcal.com/holidays/chanukah-2024',
+    'https://www.hebcal.com/holidays/chanukah-2024',
+  ];
+  expect(urls).toEqual(expected);
+});
+
 test('early-ce-url', () => {
   const ev = new HolidayEvent(new HDate(new Date(100, 8, 30)), 'Yom Kippur');
   expect(ev.url()).toBe('https://www.hebcal.com/holidays/yom-kippur-100');