diff --git a/CHANGELOG.md b/CHANGELOG.md
index 404e8c0..6845c49 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- `getStartOfDay`, `getEndOfDay` and `getLastDayOfYear` date utility functions
+
 ## [1.1.0] - 2024-10-17
 
 - export `boolean` utilities
diff --git a/src/lib/date.spec.ts b/src/lib/date.spec.ts
index 605e124..c942105 100644
--- a/src/lib/date.spec.ts
+++ b/src/lib/date.spec.ts
@@ -6,6 +6,9 @@ import {
   dateIsWeekend,
   dateDifferenceInDays,
   getNextBusinessDate,
+  getStartOfDay,
+  getEndOfDay,
+  getLastDayOfYear,
 } from "./date";
 
 describe("date tests", () => {
@@ -106,6 +109,41 @@ describe("date tests", () => {
     [42 as unknown as Date, new Date(Number.NaN)],
     ["test" as unknown as Date, new Date(Number.NaN)],
   ])("getNextBusinessDate", (date, expected) => {
-    expect(getNextBusinessDate(date).getDate()).toBe(expected.getDate());
+    expect(getNextBusinessDate(date).getTime()).toBe(expected.getTime());
+  });
+
+  test.each([
+    [new Date(2024, 0, 1, 12, 45, 25, 333), new Date(2024, 0, 1, 0, 0, 0, 0)],
+    [null as unknown as Date, new Date(Number.NaN)],
+    [undefined as unknown as Date, new Date(Number.NaN)],
+    [42 as unknown as Date, new Date(Number.NaN)],
+    ["test" as unknown as Date, new Date(Number.NaN)],
+  ])("getStartOfDay", (date, expected) => {
+    expect(getStartOfDay(date).getTime()).toBe(expected.getTime());
+  });
+
+  test.each([
+    [new Date(2024, 0, 1, 12, 45, 25, 333), new Date(2024, 0, 1, 23, 59, 59, 999)],
+    [null as unknown as Date, new Date(Number.NaN)],
+    [undefined as unknown as Date, new Date(Number.NaN)],
+    [42 as unknown as Date, new Date(Number.NaN)],
+    ["test" as unknown as Date, new Date(Number.NaN)],
+  ])("getEndOfDay", (date, expected) => {
+    expect(getEndOfDay(date).getTime()).toBe(expected.getTime());
+  });
+
+  test.each([
+    [null as unknown as Date, new Date(Number.NaN)],
+    [undefined as unknown as Date, new Date(Number.NaN)],
+    [42 as unknown as Date, new Date(Number.NaN)],
+    ["test" as unknown as Date, new Date(Number.NaN)],
+  ])("getLastDayOfYear", (date, expected) => {
+    expect(getLastDayOfYear(date).getTime()).toBe(expected.getTime());
+  });
+
+  test("getLastDayOfYear all days", () => {
+    for (let date = new Date(2024, 0, 1); date < new Date(2025, 0, 1); date.setDate(date.getDate() + 1)) {
+      expect(getLastDayOfYear(date).getTime()).toBe(new Date(2024, 11, 31, 0, 0, 0, 0).getTime());
+    }
   });
 });
diff --git a/src/lib/date.ts b/src/lib/date.ts
index fa6277b..c185ca7 100644
--- a/src/lib/date.ts
+++ b/src/lib/date.ts
@@ -7,6 +7,9 @@ import {
   isWeekend,
   differenceInCalendarDays,
   addBusinessDays,
+  startOfDay,
+  endOfDay,
+  lastDayOfYear,
 } from "date-fns";
 
 /**
@@ -73,3 +76,30 @@ export function dateDifferenceInDays(from: Date, to: Date): number {
 export function getNextBusinessDate(date: Date): Date {
   return dateIsValid(date) ? addBusinessDays(date, 1) : new Date(Number.NaN);
 }
+
+/**
+ * Get the start of a day for the given date
+ * @param date The date
+ * @returns The start of a day date
+ */
+export function getStartOfDay(date: Date): Date {
+  return dateIsValid(date) ? startOfDay(date) : new Date(Number.NaN);
+}
+
+/**
+ * Get the end of a day for the given date
+ * @param date The date
+ * @returns The end of a day date
+ */
+export function getEndOfDay(date: Date): Date {
+  return dateIsValid(date) ? endOfDay(date) : new Date(Number.NaN);
+}
+
+/**
+ * Get the last day of a year for the given date
+ * @param date The date
+ * @returns The last day of the date year
+ */
+export function getLastDayOfYear(date: Date): Date {
+  return dateIsValid(date) ? lastDayOfYear(date) : new Date(Number.NaN);
+}