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diff --git a/date-fns/src/startOfHour/index.ts b/date-fns/src/startOfHour/index.ts
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+++ b/date-fns/src/startOfHour/index.ts
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+import toDate from '../toDate/index'
+import requiredArgs from '../_lib/requiredArgs/index'
+
+/**
+ * @name startOfHour
+ * @category Hour Helpers
+ * @summary Return the start of an hour for the given date.
+ *
+ * @description
+ * Return the start of an hour for the given date.
+ * The result will be in the local timezone.
+ *
+ * ### 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 start of an hour
+ * @throws {TypeError} 1 argument required
+ *
+ * @example
+ * // The start of an hour for 2 September 2014 11:55:00:
+ * const result = startOfHour(new Date(2014, 8, 2, 11, 55))
+ * //=> Tue Sep 02 2014 11:00:00
+ */
+export default function startOfHour(dirtyDate: Date | number): Date {
+  requiredArgs(1, arguments)
+
+  const date = toDate(dirtyDate)
+  date.setMinutes(0, 0, 0)
+  return date
+}