diff --git a/utils/format-date-time.test.ts b/utils/format-date-time.test.ts
new file mode 100644
index 00000000..c3d89d9f
--- /dev/null
+++ b/utils/format-date-time.test.ts
@@ -0,0 +1,78 @@
+ 
+import { formatDateTime } from "./format-date-time";
+
+describe("formatDateTime", () => {
+  // ===== solitary =====
+  // We isolate the function from the JS runtime's locale implementation by mocking toLocaleDateString.
+  // This ensures we are testing the logic of option passing and string manipulation, not the Intl API itself.
+
+  it("calls toLocaleDateString with time options when includeTime is true", () => {
+    const spy = jest.spyOn(Date.prototype, "toLocaleDateString").mockReturnValue("Sat, Mar 23, 12:00 PM");
+
+    const result = formatDateTime("2024-03-23T12:00:00", { includeTime: true });
+
+    expect(spy).toHaveBeenCalledWith("en-US", expect.objectContaining({
+      weekday: "short",
+      month: "short",
+      day: "numeric",
+      hour: "numeric",
+      minute: "2-digit",
+      hour12: true
+    }));
+    expect(result).toBe("Sat Mar 23 12:00 PM");
+    spy.mockRestore();
+  });
+
+  it("calls toLocaleDateString with year options when includeTime is false", () => {
+    const spy = jest.spyOn(Date.prototype, "toLocaleDateString").mockReturnValue("Sat, Mar 23, 2024");
+
+    const result = formatDateTime("2024-03-23T12:00:00", { includeTime: false });
+
+    expect(spy).toHaveBeenCalledWith("en-US", expect.objectContaining({
+      weekday: "short",
+      month: "short",
+      day: "numeric",
+      year: "numeric"
+    }));
+    expect(result).toBe("Sat Mar 23 2024");
+    spy.mockRestore();
+  });
+
+  // ===== sociable =====
+  // We use real Date and Intl objects to ensure the function works correctly with the actual JS runtime.
+  // We use date strings without timezone offsets to ensure deterministic results across different environments.
+
+  it("formats date and time by default (includeTime: true)", () => {
+    // Verify that a valid date string is formatted with weekday, month, day, and time
+    const date = "2024-03-23T12:00:00";
+    expect(formatDateTime(date)).toBe("Sat Mar 23 12:00 PM");
+  });
+
+  it("formats date and time when includeTime is explicitly true", () => {
+    // Verify that explicitly passing includeTime: true produces the same result as default
+    const date = "2024-03-23T12:00:00";
+    expect(formatDateTime(date, { includeTime: true })).toBe("Sat Mar 23 12:00 PM");
+  });
+
+  it("formats date and year when includeTime is false", () => {
+    // Verify that when includeTime is false, time is omitted and year is included
+    const date = "2024-03-23T12:00:00";
+    expect(formatDateTime(date, { includeTime: false })).toBe("Sat Mar 23 2024");
+  });
+
+  it("handles invalid date strings gracefully", () => {
+    // Verify that an invalid date string returns 'Invalid Date'
+    expect(formatDateTime("not-a-date")).toBe("Invalid Date");
+  });
+
+  it("handles empty date strings gracefully", () => {
+    // Verify that an empty date string returns 'Invalid Date'
+    expect(formatDateTime("")).toBe("Invalid Date");
+  });
+
+  it("handles null or undefined date strings", () => {
+    // Verify that null or undefined (cast to any) returns 'Invalid Date'
+    expect(formatDateTime(null as any)).toBe("Invalid Date");
+    expect(formatDateTime(undefined as any)).toBe("Invalid Date");
+  });
+});
diff --git a/utils/format-date-time.ts b/utils/format-date-time.ts
index 58ad3afd..7f6b84a3 100644
--- a/utils/format-date-time.ts
+++ b/utils/format-date-time.ts
@@ -2,14 +2,17 @@
  * Format date string to readable format
  */
 export function formatDateTime(dateString: string, options: { includeTime?: boolean } = { includeTime: true }): string {
+  if (!dateString) {
+    return "Invalid Date";
+  }
   const date = new Date(dateString);
-  
+
   const formatOptions: Intl.DateTimeFormatOptions = {
     weekday: "short", // "Sun"
     month: "short", // "Mar"
     day: "numeric", // "23"
   };
-  
+
   if (options.includeTime) {
     formatOptions.hour = "numeric"; // "4"
     formatOptions.minute = "2-digit"; // "13"
@@ -17,9 +20,9 @@ export function formatDateTime(dateString: string, options: { includeTime?: bool
   } else {
     formatOptions.year = "numeric"; // "2024"
   }
-  
+
   return date
     .toLocaleDateString("en-US", formatOptions)
-    .replace(",", "")
+    .replace(/,/g, "")
     .replace(/\s+/g, " ");
 }