diff --git a/lib/private/Authentication/Login/SetUserTimezoneCommand.php b/lib/private/Authentication/Login/SetUserTimezoneCommand.php
index 90bc444ae7d..ea80fbfc714 100644
--- a/lib/private/Authentication/Login/SetUserTimezoneCommand.php
+++ b/lib/private/Authentication/Login/SetUserTimezoneCommand.php
@@ -8,6 +8,8 @@ declare(strict_types=1);
  */
 namespace OC\Authentication\Login;
 
+use OC\Core\AppInfo\Application;
+use OC\Core\AppInfo\ConfigLexicon;
 use OCP\IConfig;
 use OCP\ISession;
 
@@ -26,12 +28,10 @@ class SetUserTimezoneCommand extends ALoginCommand {
 
 	public function process(LoginData $loginData): LoginResult {
 		if ($loginData->getTimeZoneOffset() !== '' && $this->isValidTimezone($loginData->getTimeZone())) {
-			$this->config->setUserValue(
-				$loginData->getUser()->getUID(),
-				'core',
-				'timezone',
-				$loginData->getTimeZone()
-			);
+			$userId = $loginData->getUser()->getUID();
+			if ($this->config->getUserValue($userId, Application::APP_ID, ConfigLexicon::USER_TIMEZONE, '') === '') {
+				$this->config->setUserValue($userId, Application::APP_ID, ConfigLexicon::USER_TIMEZONE, $loginData->getTimeZone());
+			}
 			$this->session->set(
 				'timezone',
 				$loginData->getTimeZoneOffset()
diff --git a/tests/lib/Authentication/Login/SetUserTimezoneCommandTest.php b/tests/lib/Authentication/Login/SetUserTimezoneCommandTest.php
index fb8240c4b1e..473d14daddf 100644
--- a/tests/lib/Authentication/Login/SetUserTimezoneCommandTest.php
+++ b/tests/lib/Authentication/Login/SetUserTimezoneCommandTest.php
@@ -15,11 +15,10 @@ use OCP\ISession;
 use PHPUnit\Framework\MockObject\MockObject;
 
 class SetUserTimezoneCommandTest extends ALoginTestCommand {
-	/** @var IConfig|MockObject */
-	private $config;
 
-	/** @var ISession|MockObject */
-	private $session;
+	private IConfig&MockObject $config;
+
+	private ISession&MockObject $session;
 
 	protected function setUp(): void {
 		parent::setUp();
@@ -50,6 +49,15 @@ class SetUserTimezoneCommandTest extends ALoginTestCommand {
 		$this->user->expects($this->once())
 			->method('getUID')
 			->willReturn($this->username);
+		$this->config->expects($this->once())
+			->method('getUserValue')
+			->with(
+				$this->username,
+				'core',
+				'timezone',
+				''
+			)
+			->willReturn('');
 		$this->config->expects($this->once())
 			->method('setUserValue')
 			->with(
@@ -69,4 +77,32 @@ class SetUserTimezoneCommandTest extends ALoginTestCommand {
 
 		$this->assertTrue($result->isSuccess());
 	}
+
+	public function testProcessAlreadySet(): void {
+		$data = $this->getLoggedInLoginDataWithTimezone();
+		$this->user->expects($this->once())
+			->method('getUID')
+			->willReturn($this->username);
+		$this->config->expects($this->once())
+			->method('getUserValue')
+			->with(
+				$this->username,
+				'core',
+				'timezone',
+				'',
+			)
+			->willReturn('Europe/Berlin');
+		$this->config->expects($this->never())
+			->method('setUserValue');
+		$this->session->expects($this->once())
+			->method('set')
+			->with(
+				'timezone',
+				$this->timeZoneOffset
+			);
+
+		$result = $this->cmd->process($data);
+
+		$this->assertTrue($result->isSuccess());
+	}
 }