diff --git a/__test__/components/Menubar.test.tsx b/__test__/components/Menubar.test.tsx
index 896d43e..55a5d6c 100644
--- a/__test__/components/Menubar.test.tsx
+++ b/__test__/components/Menubar.test.tsx
@@ -55,6 +55,139 @@ describe("Calendar App Component Display Tests", () => {
     expect(screen.getByText("t")).toBeInTheDocument();
   });
 
+  // Edge cases for avatar display logic
+  it("handles user with only family_name", () => {
+    (window as any).appList = [{ name: "test", icon: "test", link: "test" }];
+    const preloadedState = {
+      user: {
+        userData: {
+          sub: "test",
+          email: "test@test.com",
+          family_name: "Smith",
+          name: null,
+          sid: "mockSid",
+          openpaasId: "667037022b752d0026472254",
+        },
+      },
+    };
+    renderWithProviders(<Menubar />, preloadedState);
+    expect(screen.getByText("t")).toBeInTheDocument();
+  });
+
+  it("handles user with only name", () => {
+    (window as any).appList = [{ name: "test", icon: "test", link: "test" }];
+    const preloadedState = {
+      user: {
+        userData: {
+          sub: "test",
+          email: "test@test.com",
+          family_name: null,
+          name: "John",
+          sid: "mockSid",
+          openpaasId: "667037022b752d0026472254",
+        },
+      },
+    };
+    renderWithProviders(<Menubar />, preloadedState);
+    expect(screen.getByText("t")).toBeInTheDocument();
+  });
+
+  it("handles user with both name and family_name", () => {
+    (window as any).appList = [{ name: "test", icon: "test", link: "test" }];
+    const preloadedState = {
+      user: {
+        userData: {
+          sub: "test",
+          email: "test@test.com",
+          family_name: "Doe",
+          name: "John",
+          sid: "mockSid",
+          openpaasId: "667037022b752d0026472254",
+        },
+      },
+    };
+    renderWithProviders(<Menubar />, preloadedState);
+    expect(screen.getByText("JD")).toBeInTheDocument();
+  });
+
+  it("handles user with no name and family_name", () => {
+    (window as any).appList = [{ name: "test", icon: "test", link: "test" }];
+    const preloadedState = {
+      user: {
+        userData: {
+          sub: "test",
+          email: "test@test.com",
+          family_name: null,
+          name: null,
+          sid: "mockSid",
+          openpaasId: "667037022b752d0026472254",
+        },
+      },
+    };
+    renderWithProviders(<Menubar />, preloadedState);
+    expect(screen.getByText("t")).toBeInTheDocument();
+  });
+
+  it("handles user with empty email", () => {
+    (window as any).appList = [{ name: "test", icon: "test", link: "test" }];
+    const preloadedState = {
+      user: {
+        userData: {
+          sub: "test",
+          email: "",
+          family_name: null,
+          name: null,
+          sid: "mockSid",
+          openpaasId: "667037022b752d0026472254",
+        },
+      },
+    };
+    renderWithProviders(<Menubar />, preloadedState);
+    // Should not crash and show empty string
+    const avatar = screen.getByRole("img", { hidden: true });
+    expect(avatar).toBeInTheDocument();
+  });
+
+  it("handles user with null email", () => {
+    (window as any).appList = [{ name: "test", icon: "test", link: "test" }];
+    const preloadedState = {
+      user: {
+        userData: {
+          sub: "test",
+          email: null,
+          family_name: null,
+          name: null,
+          sid: "mockSid",
+          openpaasId: "667037022b752d0026472254",
+        },
+      },
+    };
+    renderWithProviders(<Menubar />, preloadedState);
+    // Should not crash and show empty string
+    const avatar = screen.getByRole("img", { hidden: true });
+    expect(avatar).toBeInTheDocument();
+  });
+
+  it("handles user with undefined email", () => {
+    (window as any).appList = [{ name: "test", icon: "test", link: "test" }];
+    const preloadedState = {
+      user: {
+        userData: {
+          sub: "test",
+          email: undefined,
+          family_name: null,
+          name: null,
+          sid: "mockSid",
+          openpaasId: "667037022b752d0026472254",
+        },
+      },
+    };
+    renderWithProviders(<Menubar />, preloadedState);
+    // Should not crash and show empty string
+    const avatar = screen.getByRole("img", { hidden: true });
+    expect(avatar).toBeInTheDocument();
+  });
+
   it("shows AppsIcon when applist is not empty", () => {
     (window as any).appList = [{ name: "test", icon: "test", link: "test" }];
     renderWithProviders(<Menubar />, preloadedState);
diff --git a/__test__/features/Events/eventUtils.test.ts b/__test__/features/Events/eventUtils.test.ts
index 4cb01b1..da43b72 100644
--- a/__test__/features/Events/eventUtils.test.ts
+++ b/__test__/features/Events/eventUtils.test.ts
@@ -465,4 +465,168 @@ describe("calendarEventToJCal", () => {
       ])
     );
   });
+
+  // Edge cases for timezone fallback
+  it("handles invalid timezone with UTC fallback", () => {
+    const mockEvent = {
+      uid: "event-invalid-tz",
+      title: "Invalid Timezone Event",
+      start: new Date("2025-07-23T10:00:00"),
+      end: new Date("2025-07-23T11:00:00"),
+      timezone: "Invalid/Timezone",
+      allday: false,
+      attendee: [],
+    };
+
+    const result = calendarEventToJCal(mockEvent as CalendarEvent);
+
+    expect(result[0]).toBe("vcalendar");
+    const [vevent, vtimezone] = result[2];
+    expect(vevent[0]).toBe("vevent");
+    expect(vtimezone[0]).toBe("vtimezone");
+    
+    // Should use UTC timezone as fallback - check for UTC standard timezone
+    expect(vtimezone[2]).toEqual(
+      expect.arrayContaining([
+        ["standard", [
+          ["tzoffsetfrom", {}, "utc-offset", "+00:00"],
+          ["tzoffsetto", {}, "utc-offset", "+00:00"],
+          ["tzname", {}, "text", "UTC"],
+          ["dtstart", {}, "date-time", "1970-01-01T00:00:00"]
+        ], []]
+      ])
+    );
+  });
+
+  it("handles null timezone with UTC fallback", () => {
+    const mockEvent = {
+      uid: "event-null-tz",
+      title: "Null Timezone Event",
+      start: new Date("2025-07-23T10:00:00"),
+      end: new Date("2025-07-23T11:00:00"),
+      timezone: null,
+      allday: false,
+      attendee: [],
+    };
+
+    const result = calendarEventToJCal(mockEvent as CalendarEvent);
+
+    expect(result[0]).toBe("vcalendar");
+    const [vevent, vtimezone] = result[2];
+    expect(vevent[0]).toBe("vevent");
+    expect(vtimezone[0]).toBe("vtimezone");
+    
+    // Should use UTC timezone as fallback
+    expect(vtimezone[2]).toEqual(
+      expect.arrayContaining([
+        ["standard", [
+          ["tzoffsetfrom", {}, "utc-offset", "+00:00"],
+          ["tzoffsetto", {}, "utc-offset", "+00:00"],
+          ["tzname", {}, "text", "UTC"],
+          ["dtstart", {}, "date-time", "1970-01-01T00:00:00"]
+        ], []]
+      ])
+    );
+  });
+
+  it("handles undefined timezone with UTC fallback", () => {
+    const mockEvent = {
+      uid: "event-undefined-tz",
+      title: "Undefined Timezone Event",
+      start: new Date("2025-07-23T10:00:00"),
+      end: new Date("2025-07-23T11:00:00"),
+      timezone: undefined,
+      allday: false,
+      attendee: [],
+    };
+
+    const result = calendarEventToJCal(mockEvent as CalendarEvent);
+
+    expect(result[0]).toBe("vcalendar");
+    const [vevent, vtimezone] = result[2];
+    expect(vevent[0]).toBe("vevent");
+    expect(vtimezone[0]).toBe("vtimezone");
+    
+    // Should use UTC timezone as fallback
+    expect(vtimezone[2]).toEqual(
+      expect.arrayContaining([
+        ["standard", [
+          ["tzoffsetfrom", {}, "utc-offset", "+00:00"],
+          ["tzoffsetto", {}, "utc-offset", "+00:00"],
+          ["tzname", {}, "text", "UTC"],
+          ["dtstart", {}, "date-time", "1970-01-01T00:00:00"]
+        ], []]
+      ])
+    );
+  });
+
+  it("handles empty string timezone with UTC fallback", () => {
+    const mockEvent = {
+      uid: "event-empty-tz",
+      title: "Empty Timezone Event",
+      start: new Date("2025-07-23T10:00:00"),
+      end: new Date("2025-07-23T11:00:00"),
+      timezone: "",
+      allday: false,
+      attendee: [],
+    };
+
+    const result = calendarEventToJCal(mockEvent as CalendarEvent);
+
+    expect(result[0]).toBe("vcalendar");
+    const [vevent, vtimezone] = result[2];
+    expect(vevent[0]).toBe("vevent");
+    expect(vtimezone[0]).toBe("vtimezone");
+    
+    // Should use UTC timezone as fallback
+    expect(vtimezone[2]).toEqual(
+      expect.arrayContaining([
+        ["standard", [
+          ["tzoffsetfrom", {}, "utc-offset", "+00:00"],
+          ["tzoffsetto", {}, "utc-offset", "+00:00"],
+          ["tzname", {}, "text", "UTC"],
+          ["dtstart", {}, "date-time", "1970-01-01T00:00:00"]
+        ], []]
+      ])
+    );
+  });
+
+  it("handles valid timezone correctly", () => {
+    const mockEvent = {
+      uid: "event-valid-tz",
+      title: "Valid Timezone Event",
+      start: new Date("2025-07-23T10:00:00"),
+      end: new Date("2025-07-23T11:00:00"),
+      timezone: "Europe/Paris",
+      allday: false,
+      attendee: [],
+    };
+
+    const result = calendarEventToJCal(mockEvent as CalendarEvent);
+
+    expect(result[0]).toBe("vcalendar");
+    const [vevent, vtimezone] = result[2];
+    expect(vevent[0]).toBe("vevent");
+    expect(vtimezone[0]).toBe("vtimezone");
+    
+    // Should use the specified timezone - check for Europe/Paris timezone components
+    expect(vtimezone[2]).toEqual(
+      expect.arrayContaining([
+        ["daylight", [
+          ["tzoffsetfrom", {}, "utc-offset", "+01:00"],
+          ["tzoffsetto", {}, "utc-offset", "+02:00"],
+          ["tzname", {}, "text", "CEST"],
+          ["dtstart", {}, "date-time", "1970-03-29T02:00:00"],
+          ["rrule", {}, "recur", { byday: "-1SU", bymonth: 3, freq: "YEARLY" }]
+        ], []],
+        ["standard", [
+          ["tzoffsetfrom", {}, "utc-offset", "+02:00"],
+          ["tzoffsetto", {}, "utc-offset", "+01:00"],
+          ["tzname", {}, "text", "CET"],
+          ["dtstart", {}, "date-time", "1970-10-25T03:00:00"],
+          ["rrule", {}, "recur", { byday: "-1SU", bymonth: 10, freq: "YEARLY" }]
+        ], []]
+      ])
+    );
+  });
 });