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diff --git a/date-fns/src/differenceInCalendarMonths/index.ts b/date-fns/src/differenceInCalendarMonths/index.ts
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+import toDate from '../toDate/index'
+import requiredArgs from '../_lib/requiredArgs/index'
+
+/**
+ * @name differenceInCalendarMonths
+ * @category Month Helpers
+ * @summary Get the number of calendar months between the given dates.
+ *
+ * @description
+ * Get the number of calendar months between the given dates.
+ *
+ * ### 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).
+ *
+ * @param {Date|Number} dateLeft - the later date
+ * @param {Date|Number} dateRight - the earlier date
+ * @returns {Number} the number of calendar months
+ * @throws {TypeError} 2 arguments required
+ *
+ * @example
+ * // How many calendar months are between 31 January 2014 and 1 September 2014?
+ * var result = differenceInCalendarMonths(
+ *   new Date(2014, 8, 1),
+ *   new Date(2014, 0, 31)
+ * )
+ * //=> 8
+ */
+export default function differenceInCalendarMonths(
+  dirtyDateLeft: Date | number,
+  dirtyDateRight: Date | number
+): number {
+  requiredArgs(2, arguments)
+
+  const dateLeft = toDate(dirtyDateLeft)
+  const dateRight = toDate(dirtyDateRight)
+
+  const yearDiff = dateLeft.getFullYear() - dateRight.getFullYear()
+  const monthDiff = dateLeft.getMonth() - dateRight.getMonth()
+
+  return yearDiff * 12 + monthDiff
+}