diff --git a/app/Actions/Fortify/CreateNewUser.php b/app/Actions/Fortify/CreateNewUser.php
index b65e3816..935a1716 100644
--- a/app/Actions/Fortify/CreateNewUser.php
+++ b/app/Actions/Fortify/CreateNewUser.php
@@ -35,7 +35,7 @@ class CreateNewUser implements CreatesNewUsers
                 Rule::unique(User::class),
             ],
             'password' => $this->passwordRules(),
-            'timezone' => ['nullable', 'string', 'timezone'],
+            'timezone' => ['nullable', 'string', 'max:255'],
         ])->validate();
 
         $user = User::create([
@@ -43,7 +43,7 @@ class CreateNewUser implements CreatesNewUsers
             'email' => $input['email'],
             'password' => $input['password'],
             'locale' => $this->detectLocaleFromRequest(),
-            'timezone' => $input['timezone'] ?? null,
+            'timezone' => $this->normalizeTimezone($input['timezone'] ?? null),
         ]);
 
         if (! config('mail.email_verification_enabled')) {
@@ -53,6 +53,23 @@ class CreateNewUser implements CreatesNewUsers
         return $user;
     }
 
+    /**
+     * Normalize a browser-detected timezone, discarding identifiers PHP does
+     * not recognize so a hidden auto-detected field can never block registration.
+     */
+    protected function normalizeTimezone(?string $timezone): ?string
+    {
+        if ($timezone === null || $timezone === '') {
+            return null;
+        }
+
+        if (! in_array($timezone, timezone_identifiers_list(\DateTimeZone::ALL_WITH_BC), true)) {
+            return null;
+        }
+
+        return $timezone;
+    }
+
     /**
      * Detect locale from Accept-Language header.
      */
diff --git a/resources/js/pages/auth/register.tsx b/resources/js/pages/auth/register.tsx
index 10a38854..4fe59325 100644
--- a/resources/js/pages/auth/register.tsx
+++ b/resources/js/pages/auth/register.tsx
@@ -69,6 +69,8 @@ export default function Register({
                             value={detectedTimezone}
                         />
 
+                        <InputError message={errors.timezone} />
+
                         <div className="grid gap-6">
                             <div className="grid gap-2">
                                 <Label htmlFor="name">{__('Name')}</Label>
diff --git a/tests/Feature/Auth/RegistrationTest.php b/tests/Feature/Auth/RegistrationTest.php
index 8d57f7cf..26a21248 100644
--- a/tests/Feature/Auth/RegistrationTest.php
+++ b/tests/Feature/Auth/RegistrationTest.php
@@ -93,6 +93,42 @@ test('new users store their detected timezone on registration', function () {
     expect($user->timezone)->toBe('America/New_York');
 });
 
+test('new users can register with a legacy timezone alias', function () {
+    Queue::fake();
+
+    $response = $this->post(route('register.store'), [
+        'name' => 'Test User',
+        'email' => 'test@example.com',
+        'password' => 'password',
+        'password_confirmation' => 'password',
+        'timezone' => 'Asia/Calcutta',
+    ]);
+
+    $this->assertAuthenticated();
+    $response->assertRedirect(route('onboarding', absolute: false));
+
+    expect(User::where('email', 'test@example.com')->first()->timezone)
+        ->toBe('Asia/Calcutta');
+});
+
+test('new users can register when the browser sends an unrecognized timezone', function () {
+    Queue::fake();
+
+    $response = $this->post(route('register.store'), [
+        'name' => 'Test User',
+        'email' => 'test@example.com',
+        'password' => 'password',
+        'password_confirmation' => 'password',
+        'timezone' => 'Not/AZone',
+    ]);
+
+    $this->assertAuthenticated();
+    $response->assertRedirect(route('onboarding', absolute: false));
+
+    expect(User::where('email', 'test@example.com')->first()->timezone)
+        ->toBeNull();
+});
+
 test('new users can register without a timezone', function () {
     Queue::fake();