diff --git a/frontend/src/utils/formatDateTime.test.ts b/frontend/src/utils/formatDateTime.test.ts
new file mode 100644
index 0000000..421ab34
--- /dev/null
+++ b/frontend/src/utils/formatDateTime.test.ts
@@ -0,0 +1,27 @@
+import { describe, it, expect } from 'vitest';
+import formatDateTime from './formatDateTime';
+
+describe('formatDateTime', () => {
+  it('should format a valid date-time string correctly', () => {
+    const input = '2023-10-05T14:48:00';
+    const expectedOutput = '2023-10-05 14:48:00';
+    expect(formatDateTime(input)).toBe(expectedOutput);
+  });
+
+  it('should handle single-digit months and days correctly', () => {
+    const input = '2023-1-5T04:08:09';
+    const expectedOutput = '2023-1-5 04:08:09';
+    expect(formatDateTime(input)).toBe(expectedOutput);
+  });
+
+  it('should throw an error for an invalid date-time string', () => {
+    const input = '2023-10-05';
+    expect(() => formatDateTime(input)).toThrow();
+  });
+
+  it('should handle a date-time string without seconds correctly', () => {
+    const input = '2023-10-05T14:48';
+    const expectedOutput = '2023-10-05 14:48:00';
+    expect(formatDateTime(input)).toBe(expectedOutput);
+  });
+});
diff --git a/frontend/src/utils/formatDateTime.ts b/frontend/src/utils/formatDateTime.ts
index 955f4ee..229486e 100644
--- a/frontend/src/utils/formatDateTime.ts
+++ b/frontend/src/utils/formatDateTime.ts
@@ -1,7 +1,7 @@
 export default function formatDateTime(dateTimeString: string): string {
   const [date, time] = dateTimeString.split('T');
   const [year, month, day] = date.split('-');
-  const [hours, minutes, seconds] = time.split(':');
+  const [hours, minutes, seconds = '00'] = time.split(':');
 
   return `${year}-${month}-${day} ${hours}:${minutes}:${seconds}`;
 }
diff --git a/frontend/src/utils/timeAgo.test.ts b/frontend/src/utils/timeAgo.test.ts
new file mode 100644
index 0000000..fe872ce
--- /dev/null
+++ b/frontend/src/utils/timeAgo.test.ts
@@ -0,0 +1,51 @@
+import timeAgo from './timeAgo';
+
+describe('timeAgo', () => {
+  it('should return "1 second ago" for a date 1 second ago', () => {
+    const now = new Date();
+    const past = new Date(now.getTime() - 1000);
+    expect(timeAgo(past)).toBe('1 second ago');
+  });
+
+  it('should return "x seconds ago" for a date less than a minute ago', () => {
+    const now = new Date();
+    const past = new Date(now.getTime() - 45000); // 45 seconds ago
+    expect(timeAgo(past)).toBe('45 seconds ago');
+  });
+
+  it('should return "1 minute ago" for a date 1 minute ago', () => {
+    const now = new Date();
+    const past = new Date(now.getTime() - 60000); // 1 minute ago
+    expect(timeAgo(past)).toBe('1 minute ago');
+  });
+
+  it('should return "x minutes ago" for a date less than an hour ago', () => {
+    const now = new Date();
+    const past = new Date(now.getTime() - 1800000); // 30 minutes ago
+    expect(timeAgo(past)).toBe('30 minutes ago');
+  });
+
+  it('should return "1 hour ago" for a date 1 hour ago', () => {
+    const now = new Date();
+    const past = new Date(now.getTime() - 3600000); // 1 hour ago
+    expect(timeAgo(past)).toBe('1 hour ago');
+  });
+
+  it('should return "x hours ago" for a date less than a day ago', () => {
+    const now = new Date();
+    const past = new Date(now.getTime() - 7200000); // 2 hours ago
+    expect(timeAgo(past)).toBe('2 hours ago');
+  });
+
+  it('should return "1 day ago" for a date 1 day ago', () => {
+    const now = new Date();
+    const past = new Date(now.getTime() - 86400000); // 1 day ago
+    expect(timeAgo(past)).toBe('1 day ago');
+  });
+
+  it('should return "x days ago" for a date more than a day ago', () => {
+    const now = new Date();
+    const past = new Date(now.getTime() - 172800000); // 2 days ago
+    expect(timeAgo(past)).toBe('2 days ago');
+  });
+});