📝 Commit Details:

backend/node_modules/date-fns/getISOWeekYear.js

@@ -0,0 +1,53 @@
+import { constructFrom } from "./constructFrom.js";
+import { startOfISOWeek } from "./startOfISOWeek.js";
+import { toDate } from "./toDate.js";
+
+/**
+ * The {@link getISOWeekYear} function options.
+ */
+
+/**
+ * @name getISOWeekYear
+ * @category ISO Week-Numbering Year Helpers
+ * @summary Get the ISO week-numbering year of the given date.
+ *
+ * @description
+ * Get the ISO week-numbering year of the given date,
+ * which always starts 3 days before the year's first Thursday.
+ *
+ * ISO week-numbering year: http://en.wikipedia.org/wiki/ISO_week_date
+ *
+ * @param date - The given date
+ *
+ * @returns The ISO week-numbering year
+ *
+ * @example
+ * // Which ISO-week numbering year is 2 January 2005?
+ * const result = getISOWeekYear(new Date(2005, 0, 2))
+ * //=> 2004
+ */
+export function getISOWeekYear(date, options) {
+  const _date = toDate(date, options?.in);
+  const year = _date.getFullYear();
+
+  const fourthOfJanuaryOfNextYear = constructFrom(_date, 0);
+  fourthOfJanuaryOfNextYear.setFullYear(year + 1, 0, 4);
+  fourthOfJanuaryOfNextYear.setHours(0, 0, 0, 0);
+  const startOfNextYear = startOfISOWeek(fourthOfJanuaryOfNextYear);
+
+  const fourthOfJanuaryOfThisYear = constructFrom(_date, 0);
+  fourthOfJanuaryOfThisYear.setFullYear(year, 0, 4);
+  fourthOfJanuaryOfThisYear.setHours(0, 0, 0, 0);
+  const startOfThisYear = startOfISOWeek(fourthOfJanuaryOfThisYear);
+
+  if (_date.getTime() >= startOfNextYear.getTime()) {
+    return year + 1;
+  } else if (_date.getTime() >= startOfThisYear.getTime()) {
+    return year;
+  } else {
+    return year - 1;
+  }
+}
+
+// Fallback for modularized imports:
+export default getISOWeekYear;