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diff --git a/date-fns/src/endOfDecade/index.ts b/date-fns/src/endOfDecade/index.ts
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+++ b/date-fns/src/endOfDecade/index.ts
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+import toDate from '../toDate/index'
+import requiredArgs from '../_lib/requiredArgs/index'
+
+/**
+ * @name endOfDecade
+ * @category Decade Helpers
+ * @summary Return the end of a decade for the given date.
+ *
+ * @description
+ * Return the end of a decade for the given 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).
+ *
+ * @param {Date|Number} date - the original date
+ * @returns {Date} the end of a decade
+ * @param {Object} [options] - an object with options.
+ * @param {0|1|2} [options.additionalDigits=2] - passed to `toDate`. See [toDate]{@link https://date-fns.org/docs/toDate}
+ * @throws {TypeError} 1 argument required
+ * @throws {RangeError} `options.additionalDigits` must be 0, 1 or 2
+ *
+ * @example
+ * // The end of a decade for 12 May 1984 00:00:00:
+ * const result = endOfDecade(new Date(1984, 4, 12, 00, 00, 00))
+ * //=> Dec 31 1989 23:59:59.999
+ */
+export default function endOfDecade(dirtyDate: Date | number): Date {
+  requiredArgs(1, arguments)
+
+  const date = toDate(dirtyDate)
+  const year = date.getFullYear()
+  const decade = 9 + Math.floor(year / 10) * 10
+  date.setFullYear(decade, 11, 31)
+  date.setHours(23, 59, 59, 999)
+  return date
+}