diff --git a/src/index.ts b/src/index.ts
index 8ae6892..6aefa0a 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -17,11 +17,11 @@ function colombianHolidays(
 function colombianHolidays(
   year?: number,
   options?: { returnNativeDate?: boolean }
-): (ColombianHoliday | ColombianHolidayWithNativeDate)[];
+): ColombianHoliday[] | ColombianHolidayWithNativeDate[];
 function colombianHolidays(
   year: number = new Date().getFullYear(),
   { returnNativeDate = false }: { returnNativeDate?: boolean } = {}
-): unknown[] {
+): unknown {
   if (year < FIRST_HOLIDAY_YEAR || year > LAST_HOLIDAY_YEAR) {
     throw new Error(
       `The year should be between ${FIRST_HOLIDAY_YEAR} and ${LAST_HOLIDAY_YEAR}`
diff --git a/src/utils/holidaysWithinInterval.test.ts b/src/utils/holidaysWithinInterval.test.ts
index a74cc4b..ee86ace 100644
--- a/src/utils/holidaysWithinInterval.test.ts
+++ b/src/utils/holidaysWithinInterval.test.ts
@@ -61,6 +61,33 @@ describe("holidaysWithinInterval", () => {
     const result = holidaysWithinInterval({ start, end });
 
     expect(result.length).toBe(18);
+    expect(result).toEqual(
+      expect.arrayContaining([
+        expect.objectContaining({
+          date: expect.any(String),
+          celebrationDate: expect.any(String),
+        }),
+      ])
+    );
+  });
+
+  it("should return the correct number of holidays for a given year with native JS dates", () => {
+    const start = new Date("2021-01-01");
+    const end = new Date("2021-12-31");
+    const result = holidaysWithinInterval({
+      start,
+      end,
+      returnNativeDate: true,
+    });
+    expect(result.length).toBe(18);
+    expect(result).toEqual(
+      expect.arrayContaining([
+        expect.objectContaining({
+          date: expect.any(Date),
+          celebrationDate: expect.any(Date),
+        }),
+      ])
+    );
   });
 
   it("should return the correct number of holidays overlapping three years", () => {
diff --git a/src/utils/holidaysWithinInterval.ts b/src/utils/holidaysWithinInterval.ts
index a4d1fbb..2eb92b6 100644
--- a/src/utils/holidaysWithinInterval.ts
+++ b/src/utils/holidaysWithinInterval.ts
@@ -1,24 +1,42 @@
 import colombianHolidays from "..";
-import { ColombianHoliday } from "../types";
+import { ColombianHoliday, ColombianHolidayWithNativeDate } from "../types";
 
-export type Interval = {
+export function holidaysWithinInterval(options: {
   start: Date;
   end: Date;
-};
+  returnNativeDate?: false;
+}): ColombianHoliday[];
+export function holidaysWithinInterval(options: {
+  start: Date;
+  end: Date;
+  returnNativeDate?: true;
+}): ColombianHolidayWithNativeDate[];
+export function holidaysWithinInterval(options: {
+  start: Date;
+  end: Date;
+  returnNativeDate?: boolean;
+}): ColombianHoliday[] | ColombianHolidayWithNativeDate[];
 export function holidaysWithinInterval({
   start,
   end,
-}: Interval): ColombianHoliday[] {
+  returnNativeDate = false,
+}: {
+  start: Date;
+  end: Date;
+  returnNativeDate?: boolean;
+}): unknown {
   const yearEnd = new Date(end).getUTCFullYear();
   const yearStart = new Date(start).getUTCFullYear();
-  let holidays: ColombianHoliday[] = [];
 
-  for (let i = yearStart; i <= yearEnd; i += 1) {
-    holidays = holidays.concat(colombianHolidays(i));
-  }
+  const holidays = Array.from({ length: yearEnd - yearStart + 1 }, (_, i) =>
+    colombianHolidays(i + yearStart, { returnNativeDate })
+  ).flat();
 
   return holidays.filter(({ celebrationDate }) => {
-    const date = new Date(celebrationDate);
+    const date =
+      typeof celebrationDate === "string"
+        ? new Date(celebrationDate)
+        : celebrationDate;
     return date >= start && date <= end;
   });
 }
diff --git a/tsconfig.json b/tsconfig.json
index 9cec24e..19e6530 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -1,6 +1,6 @@
 {
   "compilerOptions": {
-    "target": "es2017",
+    "target": "es2019",
     "module": "CommonJS",
     "declaration": true,
     "sourceMap": true,