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diff --git a/date-fns/src/nextDay/index.ts b/date-fns/src/nextDay/index.ts
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+++ b/date-fns/src/nextDay/index.ts
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+import requiredArgs from '../_lib/requiredArgs/index'
+import getDay from '../getDay'
+import addDays from '../addDays'
+import toDate from '../toDate'
+import { Day } from '../types'
+
+const baseMap = [7, 6, 5, 4, 3, 2, 1]
+
+/**
+ * @name nextDay
+ * @category Weekday Helpers
+ * @summary When is the next day of the week?
+ *
+ * @description
+ * When is the next day of the week? 0-6 the day of the week, 0 represents Sunday.
+ *
+ * @param {Date | number} date - the date to check
+ * @param {Day} day - day of the week
+ * @returns {Date} - the date is the next day of week
+ * @throws {TypeError} - 2 arguments required
+ *
+ * @example
+ * // When is the next Monday after Mar, 20, 2020?
+ * const result = nextDay(new Date(2020, 2, 20), 1)
+ * //=> Mon Mar 23 2020 00:00:00
+ *
+ * @example
+ * // When is the next Tuesday after Mar, 21, 2020?
+ * const result = nextDay(new Date(2020, 2, 21), 2)
+ * //=> Tue Mar 24 2020 00:00:00
+ */
+export default function nextDay(date: Date | number, day: Day): Date {
+  requiredArgs(2, arguments)
+  const map = genMap(day)
+  return addDays(toDate(date), map[getDay(toDate(date))])
+}
+
+function genMap(daysToMove: number): number[] {
+  if (daysToMove === 0) {
+    return baseMap
+  } else {
+    const mapStart = baseMap.slice(-daysToMove)
+    const mapEnd = baseMap.slice(0, baseMap.length - daysToMove)
+    return mapStart.concat(mapEnd)
+  }
+}