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diff --git a/date-fns/src/differenceInISOWeekYears/index.ts b/date-fns/src/differenceInISOWeekYears/index.ts
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+import toDate from '../toDate/index'
+import differenceInCalendarISOWeekYears from '../differenceInCalendarISOWeekYears/index'
+import compareAsc from '../compareAsc/index'
+import subISOWeekYears from '../subISOWeekYears/index'
+import requiredArgs from '../_lib/requiredArgs/index'
+
+/**
+ * @name differenceInISOWeekYears
+ * @category ISO Week-Numbering Year Helpers
+ * @summary Get the number of full ISO week-numbering years between the given dates.
+ *
+ * @description
+ * Get the number of full ISO week-numbering years between the given dates.
+ *
+ * ISO week-numbering year: http://en.wikipedia.org/wiki/ISO_week_date
+ *
+ * ### v2.0.0 breaking changes:
+ *
+ * - [Changes that are common for the whole library](https://github.com/date-fns/date-fns/blob/master/docs/upgradeGuide.md#Common-Changes).
+ *
+ * - The function was renamed from `differenceInISOYears` to `differenceInISOWeekYears`.
+ *   "ISO week year" is short for [ISO week-numbering year](https://en.wikipedia.org/wiki/ISO_week_date).
+ *   This change makes the name consistent with
+ *   locale-dependent week-numbering year helpers, e.g., `addWeekYears`.
+ *
+ * @param {Date|Number} dateLeft - the later date
+ * @param {Date|Number} dateRight - the earlier date
+ * @returns {Number} the number of full ISO week-numbering years
+ * @throws {TypeError} 2 arguments required
+ *
+ * @example
+ * // How many full ISO week-numbering years are between 1 January 2010 and 1 January 2012?
+ * var result = differenceInISOWeekYears(
+ *   new Date(2012, 0, 1),
+ *   new Date(2010, 0, 1)
+ * )
+ * //=> 1
+ */
+export default function differenceInISOWeekYears(
+  dirtyDateLeft: Date | number,
+  dirtyDateRight: Date | number
+): number {
+  requiredArgs(2, arguments)
+
+  let dateLeft = toDate(dirtyDateLeft)
+  const dateRight = toDate(dirtyDateRight)
+
+  const sign = compareAsc(dateLeft, dateRight)
+  const difference = Math.abs(
+    differenceInCalendarISOWeekYears(dateLeft, dateRight)
+  )
+  dateLeft = subISOWeekYears(dateLeft, sign * difference)
+
+  // Math.abs(diff in full ISO years - diff in calendar ISO years) === 1
+  // if last calendar ISO year is not full
+  // If so, result must be decreased by 1 in absolute value
+  const isLastISOWeekYearNotFull = Number(
+    compareAsc(dateLeft, dateRight) === -sign
+  )
+  const result = sign * (difference - isLastISOWeekYearNotFull)
+  // Prevent negative zero
+  return result === 0 ? 0 : result
+}