diff --git a/composer.json b/composer.json
index 322ee9c..bbcfaf0 100644
--- a/composer.json
+++ b/composer.json
@@ -9,6 +9,7 @@
         "driftingly/rector-laravel": "^2.5",
         "laravel/framework": "^13.24",
         "laravel/sanctum": "^4.0",
+        "psr/clock": "^1.0",
         "sentry/sentry-laravel": "^4.27",
         "webmozart/assert": "^2.4"
     },
diff --git a/composer.lock b/composer.lock
index e61673e..e1623fd 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4,7 +4,7 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
         "This file is @generated automatically"
     ],
-    "content-hash": "3a952adbc7384cb3807e6f51d0759b30",
+    "content-hash": "77208225d86ec68b27b8bc68f441a9fa",
     "packages": [
         {
             "name": "brick/math",
diff --git a/src/Application/Security/Models/Entities/Client.php b/src/Application/Security/Models/Entities/Client.php
index d258ac1..e6a3725 100644
--- a/src/Application/Security/Models/Entities/Client.php
+++ b/src/Application/Security/Models/Entities/Client.php
@@ -10,6 +10,7 @@ use Application\Security\Models\ValueObjects\ClientSecret;
 use Application\Security\Models\ValueObjects\Entities\ClientId;
 use Shared\DDD\Model\Entity;
 use Shared\DDD\Model\HasTimestampIdentifier;
+use Shared\Time\Utc;
 
 /**
  * @implements Entity<ClientId>
@@ -17,9 +18,9 @@ use Shared\DDD\Model\HasTimestampIdentifier;
 final class Client implements Entity, HasTimestampIdentifier
 {
     private function __construct(
-        public ClientId $id,
-        public ClientIdentifier $identifier,
-        public ClientName $name,
+        public readonly ClientId $id,
+        public readonly ClientIdentifier $identifier,
+        public readonly ClientName $name,
         public ClientSecret $secret,
         public bool $isActive,
         public \DateTimeInterface $updatedAt,
@@ -44,7 +45,7 @@ final class Client implements Entity, HasTimestampIdentifier
         ClientIdentifier $identifier,
         ClientSecret $secret,
     ): self {
-        $now = new \DateTimeImmutable();
+        $now = Utc::now();
 
         return new self(
             id: $id,
@@ -77,13 +78,13 @@ final class Client implements Entity, HasTimestampIdentifier
     public function regenerateSecret(ClientSecret $newSecret): void
     {
         $this->secret    = $newSecret;
-        $this->updatedAt = new \DateTimeImmutable();
+        $this->updatedAt = Utc::now();
     }
 
     public function setActive(bool $status): bool
     {
         $this->isActive  = $status;
-        $this->updatedAt = new \DateTimeImmutable();
+        $this->updatedAt = Utc::now();
 
         return $this->isActive;
     }
diff --git a/src/Application/Security/Usecases/CreateClient/CreateClient.php b/src/Application/Security/Usecases/CreateClient/CreateClient.php
index c660c0e..05960d4 100644
--- a/src/Application/Security/Usecases/CreateClient/CreateClient.php
+++ b/src/Application/Security/Usecases/CreateClient/CreateClient.php
@@ -15,6 +15,7 @@ use Shared\DDD\Event\DomainEventDispatcher;
 use Shared\DDD\Usecase\Input as BaseInput;
 use Shared\DDD\Usecase\Transactional;
 use Shared\DDD\Usecase\Usecase;
+use Shared\Time\Utc;
 use Webmozart\Assert\Assert;
 
 /** @implements Usecase<\Application\Security\Usecases\CreateClient\Input, \Application\Security\Usecases\CreateClient\Output> */
@@ -52,7 +53,7 @@ final readonly class CreateClient implements Transactional, Usecase
         $this->dispatcher->dispatch(new ClientSecretGenerated(
             $client->id,
             $client->identifier,
-            new \DateTimeImmutable(),
+            Utc::now(),
         ));
 
         return new Output(
diff --git a/src/Application/Security/Usecases/GetSecurityAuditLogs/GetSecurityAuditLogs.php b/src/Application/Security/Usecases/GetSecurityAuditLogs/GetSecurityAuditLogs.php
index 166f03f..8d1bf08 100644
--- a/src/Application/Security/Usecases/GetSecurityAuditLogs/GetSecurityAuditLogs.php
+++ b/src/Application/Security/Usecases/GetSecurityAuditLogs/GetSecurityAuditLogs.php
@@ -7,6 +7,7 @@ namespace Application\Security\Usecases\GetSecurityAuditLogs;
 use Application\Security\Ports\Directories\ClientAuditLogDirectory;
 use Shared\DDD\Usecase\Input as BaseInput;
 use Shared\DDD\Usecase\Usecase;
+use Shared\Time\Utc;
 use Webmozart\Assert\Assert;
 
 /** @implements Usecase<\Application\Security\Usecases\GetSecurityAuditLogs\Input, \Application\Security\Usecases\GetSecurityAuditLogs\Output> */
@@ -22,7 +23,7 @@ final readonly class GetSecurityAuditLogs implements Usecase
     {
         Assert::isInstanceOf($input, Input::class);
 
-        $to = $input->to ?? new \DateTimeImmutable();
+        $to = $input->to ?? Utc::now();
 
         $entries = $this->auditLogDirectory->findLogs(
             since: $input->since,
diff --git a/src/Application/Security/Usecases/RegenerateClientSecret/RegenerateClientSecret.php b/src/Application/Security/Usecases/RegenerateClientSecret/RegenerateClientSecret.php
index 1b1947a..984cceb 100644
--- a/src/Application/Security/Usecases/RegenerateClientSecret/RegenerateClientSecret.php
+++ b/src/Application/Security/Usecases/RegenerateClientSecret/RegenerateClientSecret.php
@@ -12,6 +12,7 @@ use Shared\DDD\Event\DomainEventDispatcher;
 use Shared\DDD\Usecase\Input as BaseInput;
 use Shared\DDD\Usecase\Transactional;
 use Shared\DDD\Usecase\Usecase;
+use Shared\Time\Utc;
 use Webmozart\Assert\Assert;
 
 /** @implements Usecase<\Application\Security\Usecases\RegenerateClientSecret\Input, \Application\Security\Usecases\RegenerateClientSecret\Output> */
@@ -37,7 +38,7 @@ final readonly class RegenerateClientSecret implements Transactional, Usecase
         $this->dispatcher->dispatch(new ClientSecretRegenerated(
             $client->id,
             $client->identifier,
-            new \DateTimeImmutable(),
+            Utc::now(),
         ));
 
         return new Output($newSecret, $client->identifier);
diff --git a/src/Application/Security/Usecases/ToggleClientStatus/SetClientStatus.php b/src/Application/Security/Usecases/ToggleClientStatus/SetClientStatus.php
index 7686c4f..bb6a25d 100644
--- a/src/Application/Security/Usecases/ToggleClientStatus/SetClientStatus.php
+++ b/src/Application/Security/Usecases/ToggleClientStatus/SetClientStatus.php
@@ -11,6 +11,7 @@ use Shared\DDD\Event\DomainEventDispatcher;
 use Shared\DDD\Usecase\Input as BaseInput;
 use Shared\DDD\Usecase\Transactional;
 use Shared\DDD\Usecase\Usecase;
+use Shared\Time\Utc;
 use Webmozart\Assert\Assert;
 
 /** @implements Usecase<\Application\Security\Usecases\ToggleClientStatus\Input, \Application\Security\Usecases\ToggleClientStatus\Output> */
@@ -40,7 +41,7 @@ final readonly class SetClientStatus implements Transactional, Usecase
                 clientId: $client->id,
                 clientIdentifier: $client->identifier,
                 isActive: $isActive,
-                toggledAt: new \DateTimeImmutable(),
+                toggledAt: Utc::now(),
             ));
         }
 
diff --git a/src/Infra/Adapters/Directories/EloquentEmployeeDirectory.php b/src/Infra/Adapters/Directories/EloquentEmployeeDirectory.php
index dc5293a..cf17252 100644
--- a/src/Infra/Adapters/Directories/EloquentEmployeeDirectory.php
+++ b/src/Infra/Adapters/Directories/EloquentEmployeeDirectory.php
@@ -87,9 +87,7 @@ final class EloquentEmployeeDirectory implements EmployeeDirectory
 
     private function toDomain(EmployeeModel $employee): Employee
     {
-        $createdAt = $this->toNullableDateTime($employee->created_at);
-
-        if ($createdAt === null) {
+        if ($employee->created_at === null) {
             throw new \UnexpectedValueException('Employee created_at cannot be null.');
         }
 
@@ -97,35 +95,17 @@ final class EloquentEmployeeDirectory implements EmployeeDirectory
             publicEmployeeNumber: new ArcadiaEmployeeId((string) $employee->public_employee_number),
             lastName: (string) $employee->last_name,
             firstName: (string) $employee->first_name,
-            startDate: $this->toDateTime($employee->start_date),
-            endDate: $this->toNullableDateTime($employee->end_date),
-            plannedEndDate: $this->toNullableDateTime($employee->planned_end_date),
+            startDate: $employee->start_date,
+            endDate: $employee->end_date,
+            plannedEndDate: $employee->planned_end_date,
             establishment: new EstablishmentCode((string) $employee->establishment),
             site: new SiteId((string) $employee->site),
             service: new ServiceId((string) $employee->service),
-            createdAt: $createdAt,
-            updatedAt: $this->toNullableDateTime($employee->updated_at),
+            createdAt: $employee->created_at,
+            updatedAt: $employee->updated_at,
         );
     }
 
-    private function toDateTime(\DateTimeInterface | string $value): \DateTimeInterface
-    {
-        if ($value instanceof \DateTimeInterface) {
-            return $value;
-        }
-
-        return new \DateTimeImmutable($value);
-    }
-
-    private function toNullableDateTime(\DateTimeInterface | string | null $value): ?\DateTimeInterface
-    {
-        if ($value === null) {
-            return null;
-        }
-
-        return $this->toDateTime($value);
-    }
-
     private function toSqlColumn(EmployeeSortColumn $sortBy): string
     {
         return match ($sortBy) {
diff --git a/src/Infra/Adapters/Services/TimestampValidatorImpl.php b/src/Infra/Adapters/Services/TimestampValidatorImpl.php
index 4983ccd..dc6b624 100644
--- a/src/Infra/Adapters/Services/TimestampValidatorImpl.php
+++ b/src/Infra/Adapters/Services/TimestampValidatorImpl.php
@@ -5,11 +5,13 @@ declare(strict_types=1);
 namespace Infra\Adapters\Services;
 
 use Application\Security\Ports\Services\TimestampValidator;
+use Shared\Time\Clock;
 
 final readonly class TimestampValidatorImpl implements TimestampValidator
 {
     public function __construct(
-        private \DateTimeZone $timezone
+        private \DateTimeZone $timezone,
+        private Clock $clock,
     ) {
     }
 
@@ -30,7 +32,7 @@ final readonly class TimestampValidatorImpl implements TimestampValidator
 
     private function getCurrentTime(): \DateTimeImmutable
     {
-        return new \DateTimeImmutable('now', $this->timezone);
+        return $this->clock->now()->setTimezone($this->timezone);
     }
 
     private function getAllowedSkew(): \DateInterval
diff --git a/src/Infra/Casts/UtcDateTimeCast.php b/src/Infra/Casts/UtcDateTimeCast.php
new file mode 100644
index 0000000..cecd4ba
--- /dev/null
+++ b/src/Infra/Casts/UtcDateTimeCast.php
@@ -0,0 +1,75 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Infra\Casts;
+
+use Illuminate\Contracts\Database\Eloquent\CastsAttributes;
+use Illuminate\Database\Eloquent\Model;
+use Shared\Time\Utc;
+
+/** @implements CastsAttributes<\DateTimeImmutable|null, string|\DateTimeInterface|null> */
+final class UtcDateTimeCast implements CastsAttributes
+{
+    /**
+     * Cast the given value from the database to DateTimeImmutable in UTC.
+     *
+     * @param  array<string, mixed>  $attributes
+     */
+    #[\Override]
+    public function get(Model $model, string $key, mixed $value, array $attributes): ?\DateTimeImmutable
+    {
+        if ($value === null) {
+            return null;
+        }
+
+        if ($value instanceof \DateTimeImmutable) {
+            return $value->setTimezone(new \DateTimeZone('UTC'));
+        }
+
+        if ($value instanceof \DateTimeInterface) {
+            return \DateTimeImmutable::createFromInterface($value)->setTimezone(new \DateTimeZone('UTC'));
+        }
+
+        if (is_string($value)) {
+            $trimmed = trim($value);
+            if ($trimmed === '') {
+                return null;
+            }
+
+            return Utc::parse($trimmed);
+        }
+
+        return null;
+    }
+
+    /**
+     * Prepare the given value for storage in database format (Y-m-d H:i:s in UTC).
+     *
+     * @param  array<string, mixed>  $attributes
+     */
+    #[\Override]
+    public function set(Model $model, string $key, mixed $value, array $attributes): ?string
+    {
+        if ($value === null) {
+            return null;
+        }
+
+        if ($value instanceof \DateTimeInterface) {
+            return \DateTimeImmutable::createFromInterface($value)
+                ->setTimezone(new \DateTimeZone('UTC'))
+                ->format('Y-m-d H:i:s');
+        }
+
+        if (is_string($value)) {
+            $trimmed = trim($value);
+            if ($trimmed === '') {
+                return null;
+            }
+
+            return Utc::parse($trimmed)->format('Y-m-d H:i:s');
+        }
+
+        throw new \InvalidArgumentException(sprintf('Cannot cast value of type %s to UTC datetime', get_debug_type($value)));
+    }
+}
diff --git a/src/Infra/Database/Models/ApiClient.php b/src/Infra/Database/Models/ApiClient.php
index 942e0e8..90ab502 100644
--- a/src/Infra/Database/Models/ApiClient.php
+++ b/src/Infra/Database/Models/ApiClient.php
@@ -12,6 +12,7 @@ use Illuminate\Notifications\Notifiable;
 use Infra\Casts\ClientIdentifierCast;
 use Infra\Casts\ClientNameCast;
 use Infra\Casts\ClientSecretCast;
+use Infra\Casts\UtcDateTimeCast;
 use Infra\Casts\UuidCast;
 
 /**
@@ -21,7 +22,7 @@ use Infra\Casts\UuidCast;
  * @property \Application\Security\Models\ValueObjects\ClientIdentifier $identifier ENCRYPTED, Unique identifier that should not change
  * @property \Application\Security\Models\ValueObjects\ClientSecret $secret ENCRYPTED, api secret that can be regenerated
  * @property bool $is_active Defines if the client can be used in order to gain access to the system
- * @property \Illuminate\Support\Carbon $updated_at
+ * @property \DateTimeImmutable $updated_at
  * @property-read \Illuminate\Notifications\DatabaseNotificationCollection<int, \Illuminate\Notifications\DatabaseNotification> $notifications
  *
  * @method static \Database\Factories\ApiClientFactory factory($count = null, $state = [])
@@ -71,7 +72,7 @@ final class ApiClient extends Authenticatable
             'identifier' => ClientIdentifierCast::class,
             'secret'     => ClientSecretCast::class,
             'is_active'  => 'boolean',
-            'updated_at' => 'datetime',
+            'updated_at' => UtcDateTimeCast::class,
         ];
     }
 }
diff --git a/src/Infra/Database/Models/ClientAuditLog.php b/src/Infra/Database/Models/ClientAuditLog.php
index acaff3c..04ddf26 100644
--- a/src/Infra/Database/Models/ClientAuditLog.php
+++ b/src/Infra/Database/Models/ClientAuditLog.php
@@ -8,6 +8,7 @@ use Illuminate\Database\Eloquent\Concerns\HasUuids;
 use Illuminate\Database\Eloquent\Model;
 use Infra\Casts\ClientIdentifierCast;
 use Infra\Casts\SecurityAuditLogDetailsCast;
+use Infra\Casts\UtcDateTimeCast;
 use Infra\Casts\UuidCast;
 
 /**
@@ -16,7 +17,7 @@ use Infra\Casts\UuidCast;
  * @property \Application\Security\Models\ValueObjects\ClientIdentifier $client_identifier
  * @property string $event_type
  * @property \Application\Security\Models\ValueObjects\Entities\SecurityAuditLogDetails|null $details
- * @property \Illuminate\Support\Carbon $created_at
+ * @property \DateTimeImmutable $created_at
  *
  * @mixin \Eloquent
  */
@@ -47,7 +48,7 @@ final class ClientAuditLog extends Model
             'client_id'         => UuidCast::class,
             'client_identifier' => ClientIdentifierCast::class,
             'details'           => SecurityAuditLogDetailsCast::class,
-            'created_at'        => 'datetime',
+            'created_at'        => UtcDateTimeCast::class,
         ];
     }
 }
diff --git a/src/Infra/Database/Models/Employee.php b/src/Infra/Database/Models/Employee.php
index 01a19b9..5bcf9ee 100644
--- a/src/Infra/Database/Models/Employee.php
+++ b/src/Infra/Database/Models/Employee.php
@@ -7,20 +7,21 @@ namespace Infra\Database\Models;
 use Database\Factories\EmployeeFactory;
 use Illuminate\Database\Eloquent\Factories\HasFactory;
 use Illuminate\Database\Eloquent\Model;
+use Infra\Casts\UtcDateTimeCast;
 use Infra\Config\ArcadiaStorageConfig;
 
 /**
  * @property string $public_employee_number
  * @property string $last_name
  * @property string $first_name
- * @property \Illuminate\Support\Carbon $start_date
- * @property \Illuminate\Support\Carbon|null $end_date
- * @property \Illuminate\Support\Carbon|null $planned_end_date
+ * @property \DateTimeImmutable $start_date
+ * @property \DateTimeImmutable|null $end_date
+ * @property \DateTimeImmutable|null $planned_end_date
  * @property string $establishment
  * @property string $site
  * @property string $service
- * @property \Illuminate\Support\Carbon|null $created_at
- * @property \Illuminate\Support\Carbon|null $updated_at
+ * @property \DateTimeImmutable|null $created_at
+ * @property \DateTimeImmutable|null $updated_at
  *
  * @method static \Database\Factories\EmployeeFactory factory($count = null, $state = [])
  *
@@ -71,11 +72,11 @@ final class Employee extends Model
     protected function casts(): array
     {
         return [
-            'start_date'       => 'date',
-            'end_date'         => 'date',
-            'planned_end_date' => 'date',
-            'created_at'       => 'datetime',
-            'updated_at'       => 'datetime',
+            'start_date'       => UtcDateTimeCast::class,
+            'end_date'         => UtcDateTimeCast::class,
+            'planned_end_date' => UtcDateTimeCast::class,
+            'created_at'       => UtcDateTimeCast::class,
+            'updated_at'       => UtcDateTimeCast::class,
         ];
     }
 }
diff --git a/src/Infra/Providers/AppServiceProvider.php b/src/Infra/Providers/AppServiceProvider.php
index 8a16901..d17ee21 100644
--- a/src/Infra/Providers/AppServiceProvider.php
+++ b/src/Infra/Providers/AppServiceProvider.php
@@ -30,6 +30,8 @@ class AppServiceProvider extends ServiceProvider
 
     public function boot(AppConfig $appConfig, ThrottlingConfig $throttlingConfig): void
     {
+        date_default_timezone_set($appConfig->timezone->name);
+
         $this->configureRateLimiting($throttlingConfig);
 
         ini_set('assert.active', '1');
diff --git a/src/Infra/Providers/ConfigServiceProvider.php b/src/Infra/Providers/ConfigServiceProvider.php
index 42528e1..f073531 100644
--- a/src/Infra/Providers/ConfigServiceProvider.php
+++ b/src/Infra/Providers/ConfigServiceProvider.php
@@ -13,10 +13,14 @@ use Application\Security\Models\ValueObjects\ClientIdentifier;
 use Application\Security\Models\ValueObjects\ClientName;
 use Application\Security\Models\ValueObjects\ClientSecret;
 use Application\Security\Models\ValueObjects\Entities\ClientId;
+use Illuminate\Foundation\Application;
 use Illuminate\Support\Facades\Config;
 use Illuminate\Support\ServiceProvider;
 use Infra\Config\ArcadiaStorageConfig;
+use Psr\Clock\ClockInterface;
 use Ramsey\Uuid\Uuid;
+use Shared\Time\Clock;
+use Shared\Time\SystemClock;
 use Shared\ValueObjects\Config\AppName;
 use Shared\ValueObjects\Config\AppTimezone;
 use Shared\ValueObjects\Config\Locale;
@@ -28,6 +32,18 @@ final class ConfigServiceProvider extends ServiceProvider
     #[\Override]
     public function register(): void
     {
+        $this->app->singleton(ClockInterface::class, static function (Application $app): Clock {
+            $appConfig = $app->make(AppConfig::class);
+
+            return new SystemClock($appConfig->timezone->toDateTimeZone());
+        });
+
+        $this->app->singleton(Clock::class, static function (Application $app): Clock {
+            $appConfig = $app->make(AppConfig::class);
+
+            return new SystemClock($appConfig->timezone->toDateTimeZone());
+        });
+
         $this->app->bind(SecurityAlertMailConfig::class, static function (): SecurityAlertMailConfig {
             return new SecurityAlertMailConfig(
                 recipientEmail: new Email(Config::string('mail.security_recipient', 'security@example.com')),
diff --git a/src/Infra/Providers/SecurityServiceProvider.php b/src/Infra/Providers/SecurityServiceProvider.php
index 3c5bb90..ff43d1b 100644
--- a/src/Infra/Providers/SecurityServiceProvider.php
+++ b/src/Infra/Providers/SecurityServiceProvider.php
@@ -26,6 +26,7 @@ use Presentation\Api\V1\Security\ApiUserDetailsProvider;
 use Presentation\Console\Security\ConsoleUserDetailsProvider;
 use Psr\Log\LoggerInterface;
 use Shared\DDD\Security\UserDetailsProvider;
+use Shared\Time\Clock;
 
 final class SecurityServiceProvider extends ServiceProvider
 {
@@ -49,8 +50,9 @@ final class SecurityServiceProvider extends ServiceProvider
 
         $this->app->bind(TimestampValidator::class, function (Application $app): TimestampValidatorImpl {
             $appConfig = $app->make(AppConfig::class);
+            $clock     = $app->make(Clock::class);
 
-            return new TimestampValidatorImpl($appConfig->timezone->toDateTimeZone());
+            return new TimestampValidatorImpl($appConfig->timezone->toDateTimeZone(), $clock);
         });
 
         $this->app->bind(RequestValidator::class, RequestValidatorImpl::class);
diff --git a/src/Presentation/Api/V1/Dto/Brands/BrandDto.php b/src/Presentation/Api/V1/Dto/Brands/BrandDto.php
index 96600b0..3034656 100644
--- a/src/Presentation/Api/V1/Dto/Brands/BrandDto.php
+++ b/src/Presentation/Api/V1/Dto/Brands/BrandDto.php
@@ -7,6 +7,7 @@ namespace Presentation\Api\V1\Dto\Brands;
 use Application\Arcadia\Usecase\Brands\FindAll\BrandItem;
 use Presentation\Api\V1\Contracts\ApiResponseDto;
 use Presentation\Api\V1\Presenters\Brands\BrandShowView;
+use Shared\Time\Utc;
 
 final readonly class BrandDto implements ApiResponseDto
 {
@@ -26,7 +27,7 @@ final readonly class BrandDto implements ApiResponseDto
             code: $view->code->value,
             name: $view->name->value,
             arcadiaId: $view->arcadiaId->value,
-            createdAt: $view->createdAt->format(\DateTimeInterface::ATOM),
+            createdAt: Utc::toRfc3339($view->createdAt),
         );
     }
 
@@ -37,7 +38,7 @@ final readonly class BrandDto implements ApiResponseDto
             code: $item->code->value,
             name: $item->name->value,
             arcadiaId: $item->arcadiaId->value,
-            createdAt: $item->createdAt->format(\DateTimeInterface::ATOM),
+            createdAt: Utc::toRfc3339($item->createdAt),
         );
     }
 
diff --git a/src/Presentation/Api/V1/Http/Requests/Employees/EmployeesIndexRequest.php b/src/Presentation/Api/V1/Http/Requests/Employees/EmployeesIndexRequest.php
index 65e970e..ae29155 100644
--- a/src/Presentation/Api/V1/Http/Requests/Employees/EmployeesIndexRequest.php
+++ b/src/Presentation/Api/V1/Http/Requests/Employees/EmployeesIndexRequest.php
@@ -12,8 +12,8 @@ use Domain\Models\ValueObjects\ServiceId;
 use Domain\Models\ValueObjects\SiteId;
 use Illuminate\Foundation\Http\FormRequest;
 use Illuminate\Validation\Rule;
-use Shared\Helpers\DatesHelper;
 use Shared\Pagination;
+use Shared\Time\Utc;
 
 /**
  * @method \Shared\Pagination pagination(int $defaultPageSize = 25)
@@ -49,7 +49,7 @@ final class EmployeesIndexRequest extends FormRequest
 
     public function filter(): ?EmployeeFilter
     {
-        $since         = $this->filled('since') ? DatesHelper::parseDateTime($this->string('since')->value()) : null;
+        $since         = $this->filled('since') ? Utc::parse($this->string('since')->value()) : null;
         $establishment = $this->filled('establishment') ? new EstablishmentCode($this->string('establishment')->value()) : null;
         $service       = $this->filled('serviceId') ? new ServiceId($this->string('serviceId')->value()) : null;
 
diff --git a/src/Presentation/Api/V1/Http/Requests/IncoSheets/IncoSheetsIndexRequest.php b/src/Presentation/Api/V1/Http/Requests/IncoSheets/IncoSheetsIndexRequest.php
index d203503..715e301 100644
--- a/src/Presentation/Api/V1/Http/Requests/IncoSheets/IncoSheetsIndexRequest.php
+++ b/src/Presentation/Api/V1/Http/Requests/IncoSheets/IncoSheetsIndexRequest.php
@@ -10,8 +10,8 @@ use Domain\Models\ValueObjects\Inco\IncoSheetSortColumn;
 use Domain\Models\ValueObjects\Inco\IncoSheetSorter;
 use Illuminate\Foundation\Http\FormRequest;
 use Illuminate\Validation\Rule;
-use Shared\Helpers\DatesHelper;
 use Shared\Pagination;
+use Shared\Time\Utc;
 
 /**
  * @method \Shared\Pagination pagination(int $defaultPageSize = 25)
@@ -46,7 +46,7 @@ final class IncoSheetsIndexRequest extends FormRequest
 
     public function filter(): ?IncoSheetFilter
     {
-        $since = $this->filled('since') ? DatesHelper::parseDateTime($this->string('since')->value()) : null;
+        $since = $this->filled('since') ? Utc::parse($this->string('since')->value()) : null;
 
         $brandCodes = [];
         $rawBrands  = $this->array('brands');
diff --git a/src/Presentation/Api/V1/Http/Responses/IncoSheets/IncoSheetsIndexResponse.php b/src/Presentation/Api/V1/Http/Responses/IncoSheets/IncoSheetsIndexResponse.php
index a6972a3..eabb427 100644
--- a/src/Presentation/Api/V1/Http/Responses/IncoSheets/IncoSheetsIndexResponse.php
+++ b/src/Presentation/Api/V1/Http/Responses/IncoSheets/IncoSheetsIndexResponse.php
@@ -22,6 +22,7 @@ use Presentation\Api\V1\Dto\IncoSheets\Parts\StorageConditionDto;
 use Presentation\Api\V1\Dto\IncoSheets\Parts\WeightDto;
 use Presentation\Api\V1\Dto\PaginationDto;
 use Presentation\Api\V1\Presenters\IncoSheets\IncoSheetsIndexView;
+use Shared\Time\Utc;
 use Uri\Rfc3986\Uri;
 
 final readonly class IncoSheetsIndexResponse implements ApiResponse
@@ -46,7 +47,7 @@ final readonly class IncoSheetsIndexResponse implements ApiResponse
             pageSize: $this->view->perPage,
             totalItems: $this->view->total,
             baseUri: $this->baseUri,
-        );
+        )->toArray();
 
         $items = array_map(
             fn (PaginatedIncoSheet | PaginatedShortIncoSheet $sheet): array => match (true) {
@@ -68,8 +69,8 @@ final readonly class IncoSheetsIndexResponse implements ApiResponse
             id: (string) $sheet->id,
             name: $sheet->name,
             label: $sheet->label,
-            createdAt: $sheet->createdAt?->format(\DateTimeInterface::ATOM),
-            updatedAt: $sheet->updatedAt?->format(\DateTimeInterface::ATOM),
+            createdAt: Utc::toNullableRfc3339($sheet->createdAt),
+            updatedAt: Utc::toNullableRfc3339($sheet->updatedAt),
         );
     }
 
@@ -104,8 +105,8 @@ final readonly class IncoSheetsIndexResponse implements ApiResponse
                 $sheet->additives
             )),
             compo: $sheet->compo !== null ? (string) $sheet->compo : null,
-            createdAt: $sheet->createdAt?->format(\DateTimeInterface::ATOM),
-            updatedAt: $sheet->updatedAt?->format(\DateTimeInterface::ATOM),
+            createdAt: Utc::toNullableRfc3339($sheet->createdAt),
+            updatedAt: Utc::toNullableRfc3339($sheet->updatedAt),
         );
     }
 }
diff --git a/src/Presentation/Api/V1/Http/Responses/IncoSheets/IncoSheetsSearchResponse.php b/src/Presentation/Api/V1/Http/Responses/IncoSheets/IncoSheetsSearchResponse.php
index 40c8dd0..2ca2059 100644
--- a/src/Presentation/Api/V1/Http/Responses/IncoSheets/IncoSheetsSearchResponse.php
+++ b/src/Presentation/Api/V1/Http/Responses/IncoSheets/IncoSheetsSearchResponse.php
@@ -22,6 +22,7 @@ use Presentation\Api\V1\Dto\IncoSheets\Parts\StorageConditionDto;
 use Presentation\Api\V1\Dto\IncoSheets\Parts\WeightDto;
 use Presentation\Api\V1\Dto\PaginationDto;
 use Presentation\Api\V1\Presenters\IncoSheets\IncoSheetsSearchView;
+use Shared\Time\Utc;
 use Uri\Rfc3986\Uri;
 
 final readonly class IncoSheetsSearchResponse implements ApiResponse
@@ -46,7 +47,7 @@ final readonly class IncoSheetsSearchResponse implements ApiResponse
             pageSize: $this->view->perPage,
             totalItems: $this->view->total,
             baseUri: $this->baseUri,
-        );
+        )->toArray();
 
         $items = array_map(
             fn (PaginatedIncoSheet | PaginatedShortIncoSheet $sheet): array => match (true) {
@@ -68,8 +69,8 @@ final readonly class IncoSheetsSearchResponse implements ApiResponse
             id: (string) $sheet->id,
             name: $sheet->name,
             label: $sheet->label,
-            createdAt: $sheet->createdAt?->format(\DateTimeInterface::ATOM),
-            updatedAt: $sheet->updatedAt?->format(\DateTimeInterface::ATOM),
+            createdAt: Utc::toNullableRfc3339($sheet->createdAt),
+            updatedAt: Utc::toNullableRfc3339($sheet->updatedAt),
         );
     }
 
@@ -104,8 +105,8 @@ final readonly class IncoSheetsSearchResponse implements ApiResponse
                 $sheet->additives
             )),
             compo: $sheet->compo !== null ? (string) $sheet->compo : null,
-            createdAt: $sheet->createdAt?->format(\DateTimeInterface::ATOM),
-            updatedAt: $sheet->updatedAt?->format(\DateTimeInterface::ATOM),
+            createdAt: Utc::toNullableRfc3339($sheet->createdAt),
+            updatedAt: Utc::toNullableRfc3339($sheet->updatedAt),
         );
     }
 }
diff --git a/src/Presentation/Api/V1/Http/Responses/IncoSheets/IncoSheetsShowResponse.php b/src/Presentation/Api/V1/Http/Responses/IncoSheets/IncoSheetsShowResponse.php
index b073973..60b488e 100644
--- a/src/Presentation/Api/V1/Http/Responses/IncoSheets/IncoSheetsShowResponse.php
+++ b/src/Presentation/Api/V1/Http/Responses/IncoSheets/IncoSheetsShowResponse.php
@@ -19,6 +19,7 @@ use Presentation\Api\V1\Dto\IncoSheets\Parts\PortionsDto;
 use Presentation\Api\V1\Dto\IncoSheets\Parts\StorageConditionDto;
 use Presentation\Api\V1\Dto\IncoSheets\Parts\WeightDto;
 use Presentation\Api\V1\Presenters\IncoSheets\IncoSheetsShowView;
+use Shared\Time\Utc;
 
 final readonly class IncoSheetsShowResponse implements ApiResponse
 {
@@ -72,8 +73,8 @@ final readonly class IncoSheetsShowResponse implements ApiResponse
                 $output->additives
             )),
             compo: $output->compo !== null ? (string) $output->compo : null,
-            createdAt: $output->createdAt?->format(\DateTimeInterface::ATOM),
-            updatedAt: $output->updatedAt?->format(\DateTimeInterface::ATOM),
+            createdAt: Utc::toNullableRfc3339($output->createdAt),
+            updatedAt: Utc::toNullableRfc3339($output->updatedAt),
         );
     }
 }
diff --git a/src/Presentation/Console/Commands/ExportSecurityAuditLogsCommand.php b/src/Presentation/Console/Commands/ExportSecurityAuditLogsCommand.php
index af8e8a4..a8baa3c 100644
--- a/src/Presentation/Console/Commands/ExportSecurityAuditLogsCommand.php
+++ b/src/Presentation/Console/Commands/ExportSecurityAuditLogsCommand.php
@@ -13,6 +13,7 @@ use Presentation\Console\Presenters\Security\AuditLogsPresenter;
 use Presentation\Console\Presenters\Security\AuditLogsView;
 use Shared\DDD\Usecase\Builder\UsecaseBuilder;
 use Shared\DDD\Usecase\Builder\UsecaseExecutor;
+use Shared\Time\Utc;
 
 final class ExportSecurityAuditLogsCommand extends Command
 {
@@ -23,28 +24,33 @@ final class ExportSecurityAuditLogsCommand extends Command
                             {--since= : Retrieve events occurred since this date (e.g. "2026-08-01", "-7 days")}
                             {--to= : Retrieve events occurred up to this date (defaults to now)}
                             {--client= : Filter by client ID or identifier}
-                            {--event= : Filter by event type (e.g. "client_secret_generated", "client_secret_regenerated", "client_status_toggled")}
-                            {--csv : Export output to CSV file in storage/app/audit/}';
+                            {--event= : Filter by event type}
+                            {--csv : Export output as CSV file in storage/app/audit/}';
 
     /**
      * @var string
      */
     protected $description = 'Display or export security audit events since a specified date';
 
-    public function handle(
-        GetSecurityAuditLogs $usecase,
-        UsecaseExecutor $executor,
-        AuditLogsPresenter $presenter,
-    ): int {
+    public function __construct(
+        private GetSecurityAuditLogs $usecase,
+        private UsecaseExecutor $executor,
+        private AuditLogsPresenter $presenter,
+    ) {
+        parent::__construct();
+    }
+
+    public function handle(): int
+    {
         $input = $this->buildInput();
         if ($input === null) {
             return self::FAILURE;
         }
 
-        $view = UsecaseBuilder::using($executor)
-            ->do($usecase)
+        $view = UsecaseBuilder::using($this->executor)
+            ->do($this->usecase)
             ->from($input)
-            ->with($presenter)
+            ->with($this->presenter)
             ->run();
 
         if ($this->option('csv')) {
@@ -62,7 +68,7 @@ final class ExportSecurityAuditLogsCommand extends Command
             : '-7 days';
 
         try {
-            $since = new \DateTimeImmutable($sinceString);
+            $since = Utc::parse($sinceString);
         } catch (\Exception) {
             $this->error("Invalid date format for --since: '{$sinceString}'.");
 
@@ -73,7 +79,7 @@ final class ExportSecurityAuditLogsCommand extends Command
         $to       = null;
         if (is_string($toOption) && trim($toOption) !== '') {
             try {
-                $to = new \DateTimeImmutable(trim($toOption));
+                $to = Utc::parse(trim($toOption));
             } catch (\Exception) {
                 $this->error("Invalid date format for --to: '{$toOption}'.");
 
@@ -127,7 +133,7 @@ final class ExportSecurityAuditLogsCommand extends Command
             File::makeDirectory($dir, 0755, true);
         }
 
-        $filename = sprintf('security-audit-%s.csv', (new \DateTimeImmutable())->format('Y-m-d-His'));
+        $filename = sprintf('security-audit-%s.csv', Utc::now()->format('Y-m-d-His'));
         $filePath = "{$dir}/{$filename}";
 
         File::put($filePath, $view->toCsvContent());
diff --git a/src/Presentation/Console/Presenters/Brands/ListBrandsPresenter.php b/src/Presentation/Console/Presenters/Brands/ListBrandsPresenter.php
index 9462292..6c6b2ec 100644
--- a/src/Presentation/Console/Presenters/Brands/ListBrandsPresenter.php
+++ b/src/Presentation/Console/Presenters/Brands/ListBrandsPresenter.php
@@ -8,6 +8,7 @@ use Application\Arcadia\Usecase\Brands\FindAll\BrandItem;
 use Application\Arcadia\Usecase\Brands\FindAll\Output;
 use Shared\DDD\Usecase\Output as UsecaseOutput;
 use Shared\DDD\Usecase\Presenter;
+use Shared\Time\Utc;
 use Webmozart\Assert\Assert;
 
 /** @implements Presenter<Output, ListBrandsView> */
@@ -25,7 +26,7 @@ final readonly class ListBrandsPresenter implements Presenter
                 code: $brand->code->value,
                 name: $brand->name->value,
                 arcadiaId: $brand->arcadiaId->value,
-                createdAt: $brand->createdAt->format('Y-m-d H:i:s'),
+                createdAt: Utc::toRfc3339($brand->createdAt),
             ),
             $output->brands
         ));
diff --git a/src/Presentation/Console/Presenters/Clients/ListClientsPresenter.php b/src/Presentation/Console/Presenters/Clients/ListClientsPresenter.php
index fccac4c..333dcab 100644
--- a/src/Presentation/Console/Presenters/Clients/ListClientsPresenter.php
+++ b/src/Presentation/Console/Presenters/Clients/ListClientsPresenter.php
@@ -8,6 +8,7 @@ use Application\Security\Usecases\FindAllClients\Output;
 use Application\Security\Usecases\FindAllClients\PaginatedClient;
 use Shared\DDD\Usecase\Output as UsecaseOutput;
 use Shared\DDD\Usecase\Presenter;
+use Shared\Time\Utc;
 use Webmozart\Assert\Assert;
 
 /** @implements Presenter<Output, ListClientsView> */
@@ -25,7 +26,7 @@ final readonly class ListClientsPresenter implements Presenter
                 name: $client->name->value,
                 identifier: $client->identifier->value,
                 status: $client->isActive ? 'Active' : 'Inactive',
-                lastUpdatedAt: $client->updatedAt->format('Y-m-d H:i:s'),
+                lastUpdatedAt: Utc::toRfc3339($client->updatedAt),
             ),
             $output->clients
         ));
diff --git a/src/Shared/Helpers/DatesHelper.php b/src/Shared/Helpers/DatesHelper.php
index feda33c..3c24d95 100644
--- a/src/Shared/Helpers/DatesHelper.php
+++ b/src/Shared/Helpers/DatesHelper.php
@@ -10,13 +10,13 @@ use Shared\Helpers\Exceptions\InvalidDateFormatException;
 
 final class DatesHelper
 {
-    private const string FRENCH_DATE_REGEX   = '/^\d{4}-\d{2}-\d{2}$/';
+    private const string FRENCH_DATE_REGEX = '/^\d{4}-\d{2}-\d{2}$/';
 
-    private const string FRENCH_DATE_INVERT_REGEX   = '/^\d{2}-\d{2}-\d{4}$/';
+    private const string FRENCH_DATE_INVERT_REGEX = '/^\d{2}-\d{2}-\d{4}$/';
 
-    private const string ISO8601_REGEX       = '/^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}Z$/';
+    private const string ISO8601_REGEX = '/^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}Z$/';
 
-    private const string RFC3339_REGEX       = '/^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}(?:\.\d+)?(?:Z|[+\-]\d{2}:\d{2})$/';
+    private const string RFC3339_REGEX = '/^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}(?:\.\d+)?(?:Z|[+\-]\d{2}:\d{2})$/';
 
     private function __construct()
     {
@@ -24,11 +24,11 @@ final class DatesHelper
     }
 
     /**
-     * Vérifie si la date actuelle se situe dans l'intervalle donné.
+     * Vérifie si la date actuelle se situe dans l'intervalle donné (en UTC).
      */
     public static function isIn(?CarbonInterface $from, ?CarbonInterface $to): bool
     {
-        $now = CarbonImmutable::now();
+        $now = CarbonImmutable::now(new \DateTimeZone('UTC'));
 
         return match (true) {
             $from !== null && $to !== null   => $now->between($from, $to),
@@ -40,9 +40,20 @@ final class DatesHelper
 
     public static function toRfc3339(\DateTimeInterface | string $datetime): string
     {
-        $datetime = is_string($datetime) ? self::parseDateTime($datetime) : $datetime;
+        $dt = is_string($datetime) ? self::parseDateTime($datetime) : $datetime;
 
-        return $datetime->format(\DATE_RFC3339);
+        if ($dt instanceof \DateTimeImmutable) {
+            $dt = $dt->setTimezone(new \DateTimeZone('UTC'));
+        } elseif ($dt instanceof \DateTime) {
+            $dt = (clone $dt)->setTimezone(new \DateTimeZone('UTC'));
+        }
+
+        return $dt->format(\DATE_RFC3339);
+    }
+
+    public static function toNullableRfc3339(\DateTimeInterface | string | null $datetime): ?string
+    {
+        return $datetime !== null ? self::toRfc3339($datetime) : null;
     }
 
     public static function parseDateTime(string $datetime): \DateTimeInterface
@@ -67,7 +78,7 @@ final class DatesHelper
                 break;
             default:
                 try {
-                    $output = new \DateTimeImmutable($datetime);
+                    $output = (new \DateTimeImmutable($datetime, new \DateTimeZone('UTC')))->setTimezone(new \DateTimeZone('UTC'));
                 } catch (\Exception) {
                     throw InvalidDateFormatException::forDateString($datetime);
                 }
@@ -78,41 +89,41 @@ final class DatesHelper
 
     protected static function parseFrench(string $datetime): \DateTimeInterface
     {
-        $dt = \DateTimeImmutable::createFromFormat('Y-m-d H:i:s', $datetime . ' 00:00:00');
+        $dt = \DateTimeImmutable::createFromFormat('Y-m-d H:i:s', $datetime . ' 00:00:00', new \DateTimeZone('UTC'));
 
         return $dt ?: self::parseFallback($datetime);
     }
 
     protected static function parseFrenchInverted(string $datetime): \DateTimeInterface
     {
-        $dt = \DateTimeImmutable::createFromFormat('d-m-Y H:i:s', $datetime . ' 00:00:00');
+        $dt = \DateTimeImmutable::createFromFormat('d-m-Y H:i:s', $datetime . ' 00:00:00', new \DateTimeZone('UTC'));
 
         return $dt ?: self::parseFallback($datetime);
     }
 
     protected static function parseRfc3339(string $datetime): \DateTimeInterface
     {
-        $dt = \DateTimeImmutable::createFromFormat(\DateTime::RFC3339, $datetime);
+        $dt = \DateTimeImmutable::createFromFormat(\DateTimeInterface::RFC3339, $datetime);
         if ($dt !== false) {
-            return $dt;
+            return $dt->setTimezone(new \DateTimeZone('UTC'));
         }
 
         $dt = \DateTimeImmutable::createFromFormat('Y-m-d\TH:i:s.uP', $datetime);
 
-        return $dt ?: self::parseFallback($datetime);
+        return $dt ? $dt->setTimezone(new \DateTimeZone('UTC')) : self::parseFallback($datetime);
     }
 
     protected static function parseIso8601(string $datetime): \DateTimeInterface
     {
         $dt = \DateTimeImmutable::createFromFormat(\DateTimeInterface::ATOM, $datetime);
 
-        return $dt ?: self::parseFallback($datetime);
+        return $dt ? $dt->setTimezone(new \DateTimeZone('UTC')) : self::parseFallback($datetime);
     }
 
     protected static function parseFallback(string $datetime): \DateTimeInterface
     {
         try {
-            return new \DateTimeImmutable($datetime);
+            return (new \DateTimeImmutable($datetime, new \DateTimeZone('UTC')))->setTimezone(new \DateTimeZone('UTC'));
         } catch (\Throwable) {
             throw InvalidDateFormatException::forDateString($datetime);
         }
diff --git a/src/Shared/Helpers/UuidHelper.php b/src/Shared/Helpers/UuidHelper.php
index 9a02cd3..cd4861a 100644
--- a/src/Shared/Helpers/UuidHelper.php
+++ b/src/Shared/Helpers/UuidHelper.php
@@ -79,6 +79,6 @@ final readonly class UuidHelper
             throw new InvalidUuidException("Failed to extract datetime from UUID: {$uuid->toString()}");
         }
 
-        return $dateTime;
+        return $dateTime->setTimezone(new \DateTimeZone('UTC'));
     }
 }
diff --git a/src/Shared/Time/Clock.php b/src/Shared/Time/Clock.php
new file mode 100644
index 0000000..ddd7309
--- /dev/null
+++ b/src/Shared/Time/Clock.php
@@ -0,0 +1,25 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Shared\Time;
+
+use Psr\Clock\ClockInterface;
+
+interface Clock extends ClockInterface
+{
+    #[\Override]
+    public function now(): \DateTimeImmutable;
+
+    public function parse(string $datetime): \DateTimeImmutable;
+
+    public function startOfDay(\DateTimeInterface | string $date): \DateTimeImmutable;
+
+    public function endOfDay(\DateTimeInterface | string $date): \DateTimeImmutable;
+
+    public function toIso8601(\DateTimeInterface | string $date): string;
+
+    public function toRfc3339(\DateTimeInterface | string $date): string;
+
+    public function toNullableRfc3339(\DateTimeInterface | string | null $date): ?string;
+}
diff --git a/src/Shared/Time/FrozenClock.php b/src/Shared/Time/FrozenClock.php
new file mode 100644
index 0000000..d8af806
--- /dev/null
+++ b/src/Shared/Time/FrozenClock.php
@@ -0,0 +1,86 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Shared\Time;
+
+use Shared\Helpers\DatesHelper;
+
+final class FrozenClock implements Clock
+{
+    private const string UTC = 'UTC';
+
+    private \DateTimeImmutable $now;
+
+    public function __construct(?\DateTimeInterface $now = null)
+    {
+        if ($now === null) {
+            $this->now = new \DateTimeImmutable('now', new \DateTimeZone(self::UTC));
+        } else {
+            $this->now = \DateTimeImmutable::createFromInterface($now)->setTimezone(new \DateTimeZone(self::UTC));
+        }
+    }
+
+    public function setTo(\DateTimeInterface | string $time): void
+    {
+        if (is_string($time)) {
+            $this->now = $this->parse($time);
+        } else {
+            $this->now = \DateTimeImmutable::createFromInterface($time)->setTimezone(new \DateTimeZone(self::UTC));
+        }
+    }
+
+    #[\Override]
+    public function now(): \DateTimeImmutable
+    {
+        return $this->now;
+    }
+
+    #[\Override]
+    public function parse(string $datetime): \DateTimeImmutable
+    {
+        $parsed = DatesHelper::parseDateTime($datetime);
+
+        if ($parsed instanceof \DateTimeImmutable) {
+            return $parsed->setTimezone(new \DateTimeZone(self::UTC));
+        }
+
+        return \DateTimeImmutable::createFromInterface($parsed)->setTimezone(new \DateTimeZone(self::UTC));
+    }
+
+    #[\Override]
+    public function startOfDay(\DateTimeInterface | string $date): \DateTimeImmutable
+    {
+        $dt = is_string($date) ? $this->parse($date) : $date;
+        $dt = \DateTimeImmutable::createFromInterface($dt)->setTimezone(new \DateTimeZone(self::UTC));
+
+        return $dt->setTime(0, 0, 0, 0);
+    }
+
+    #[\Override]
+    public function endOfDay(\DateTimeInterface | string $date): \DateTimeImmutable
+    {
+        $dt = is_string($date) ? $this->parse($date) : $date;
+        $dt = \DateTimeImmutable::createFromInterface($dt)->setTimezone(new \DateTimeZone(self::UTC));
+
+        return $dt->setTime(23, 59, 59, 999999);
+    }
+
+    #[\Override]
+    public function toIso8601(\DateTimeInterface | string $date): string
+    {
+        return $this->toRfc3339($date);
+    }
+
+    #[\Override]
+    public function toRfc3339(\DateTimeInterface | string $date): string
+    {
+        return DatesHelper::toRfc3339($date);
+    }
+
+    #[\Override]
+    public function toNullableRfc3339(\DateTimeInterface | string | null $date): ?string
+    {
+        return DatesHelper::toNullableRfc3339($date);
+    }
+}
diff --git a/src/Shared/Time/SystemClock.php b/src/Shared/Time/SystemClock.php
new file mode 100644
index 0000000..84e1cfc
--- /dev/null
+++ b/src/Shared/Time/SystemClock.php
@@ -0,0 +1,76 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Shared\Time;
+
+use Shared\Helpers\DatesHelper;
+
+readonly class SystemClock implements Clock
+{
+    private \DateTimeZone $timezone;
+
+    public function __construct(\DateTimeZone | string $timezone = 'UTC')
+    {
+        $this->timezone = is_string($timezone) ? new \DateTimeZone($timezone) : $timezone;
+    }
+
+    public function timezone(): \DateTimeZone
+    {
+        return $this->timezone;
+    }
+
+    #[\Override]
+    public function now(): \DateTimeImmutable
+    {
+        return new \DateTimeImmutable('now', $this->timezone);
+    }
+
+    #[\Override]
+    public function parse(string $datetime): \DateTimeImmutable
+    {
+        $parsed = DatesHelper::parseDateTime($datetime);
+
+        if ($parsed instanceof \DateTimeImmutable) {
+            return $parsed->setTimezone($this->timezone);
+        }
+
+        return \DateTimeImmutable::createFromInterface($parsed)->setTimezone($this->timezone);
+    }
+
+    #[\Override]
+    public function startOfDay(\DateTimeInterface | string $date): \DateTimeImmutable
+    {
+        $dt = is_string($date) ? $this->parse($date) : $date;
+        $dt = \DateTimeImmutable::createFromInterface($dt)->setTimezone($this->timezone);
+
+        return $dt->setTime(0, 0, 0, 0);
+    }
+
+    #[\Override]
+    public function endOfDay(\DateTimeInterface | string $date): \DateTimeImmutable
+    {
+        $dt = is_string($date) ? $this->parse($date) : $date;
+        $dt = \DateTimeImmutable::createFromInterface($dt)->setTimezone($this->timezone);
+
+        return $dt->setTime(23, 59, 59, 999999);
+    }
+
+    #[\Override]
+    public function toIso8601(\DateTimeInterface | string $date): string
+    {
+        return $this->toRfc3339($date);
+    }
+
+    #[\Override]
+    public function toRfc3339(\DateTimeInterface | string $date): string
+    {
+        return DatesHelper::toRfc3339($date);
+    }
+
+    #[\Override]
+    public function toNullableRfc3339(\DateTimeInterface | string | null $date): ?string
+    {
+        return DatesHelper::toNullableRfc3339($date);
+    }
+}
diff --git a/src/Shared/Time/SystemUtcClock.php b/src/Shared/Time/SystemUtcClock.php
new file mode 100644
index 0000000..376912c
--- /dev/null
+++ b/src/Shared/Time/SystemUtcClock.php
@@ -0,0 +1,13 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Shared\Time;
+
+final readonly class SystemUtcClock extends SystemClock
+{
+    public function __construct()
+    {
+        parent::__construct(new \DateTimeZone('UTC'));
+    }
+}
diff --git a/src/Shared/Time/Utc.php b/src/Shared/Time/Utc.php
new file mode 100644
index 0000000..5927c4e
--- /dev/null
+++ b/src/Shared/Time/Utc.php
@@ -0,0 +1,73 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Shared\Time;
+
+final class Utc
+{
+    private static ?Clock $clock = null;
+
+    private function __construct()
+    {
+        // Static utility class
+    }
+
+    public static function getClock(): Clock
+    {
+        return self::$clock ??= new SystemUtcClock();
+    }
+
+    public static function setClock(?Clock $clock): void
+    {
+        self::$clock = $clock;
+    }
+
+    public static function freeze(?\DateTimeInterface $at = null): FrozenClock
+    {
+        $frozen      = new FrozenClock($at);
+        self::$clock = $frozen;
+
+        return $frozen;
+    }
+
+    public static function restore(): void
+    {
+        self::$clock = null;
+    }
+
+    public static function now(): \DateTimeImmutable
+    {
+        return self::getClock()->now();
+    }
+
+    public static function parse(string $datetime): \DateTimeImmutable
+    {
+        return self::getClock()->parse($datetime);
+    }
+
+    public static function startOfDay(\DateTimeInterface | string $date): \DateTimeImmutable
+    {
+        return self::getClock()->startOfDay($date);
+    }
+
+    public static function endOfDay(\DateTimeInterface | string $date): \DateTimeImmutable
+    {
+        return self::getClock()->endOfDay($date);
+    }
+
+    public static function toIso8601(\DateTimeInterface | string $date): string
+    {
+        return self::getClock()->toIso8601($date);
+    }
+
+    public static function toRfc3339(\DateTimeInterface | string $date): string
+    {
+        return self::getClock()->toRfc3339($date);
+    }
+
+    public static function toNullableRfc3339(\DateTimeInterface | string | null $date): ?string
+    {
+        return self::getClock()->toNullableRfc3339($date);
+    }
+}
diff --git a/tests/Architecture/CodingStandardsTest.php b/tests/Architecture/CodingStandardsTest.php
index 232f48c..e5c2506 100644
--- a/tests/Architecture/CodingStandardsTest.php
+++ b/tests/Architecture/CodingStandardsTest.php
@@ -66,6 +66,10 @@ describe('Coding Standards & Project Rules', function (): void {
         ->expect(['sleep', 'usleep'])
         ->not->toBeUsed();
 
+    arch('mutable DateTime is not used in src (use DateTimeImmutable or DateTimeInterface)')
+        ->expect('DateTime')
+        ->not->toBeUsed();
+
     arch('all Domain source files use strict types')
         ->expect('Domain')
         ->toUseStrictTypes();
diff --git a/tests/Feature/Console/Commands/ListClientsCommandTest.php b/tests/Feature/Console/Commands/ListClientsCommandTest.php
index b8deee6..cb06df5 100644
--- a/tests/Feature/Console/Commands/ListClientsCommandTest.php
+++ b/tests/Feature/Console/Commands/ListClientsCommandTest.php
@@ -7,6 +7,7 @@ namespace Tests\Feature\Console\Commands;
 use Infra\Database\Models\ApiClient;
 use Presentation\Console\Commands\ListClientsCommand;
 use Ramsey\Uuid\Uuid;
+use Shared\Time\Utc;
 
 covers(ListClientsCommand::class);
 
@@ -57,14 +58,14 @@ describe('ListClientsCommand', function (): void {
                         (string) $client1->name->value,
                         (string) $client1->identifier->value,
                         'Active',
-                        $client1->updated_at->format('Y-m-d H:i:s'),
+                        Utc::toRfc3339($client1->updated_at),
                     ],
                     [
                         (string) $client2->id,
                         (string) $client2->name->value,
                         (string) $client2->identifier->value,
                         'Inactive',
-                        $client2->updated_at->format('Y-m-d H:i:s'),
+                        Utc::toRfc3339($client2->updated_at),
                     ],
                 ]
             )
diff --git a/tests/Integration/Infra/Adapters/Directories/EloquentEmployeeDirectoryTest.php b/tests/Integration/Infra/Adapters/Directories/EloquentEmployeeDirectoryTest.php
index bbaf98e..96b957f 100644
--- a/tests/Integration/Infra/Adapters/Directories/EloquentEmployeeDirectoryTest.php
+++ b/tests/Integration/Infra/Adapters/Directories/EloquentEmployeeDirectoryTest.php
@@ -65,20 +65,6 @@ describe('EloquentEmployeeDirectory Integration Tests', function (): void {
             ->and($result?->updatedAt?->format('Y-m-d H:i:s'))->toBe('2024-01-02 12:00:00');
     });
 
-    it('converts string dates to DateTimeInterface using toDateTime helper', function (): void {
-        // GIVEN
-        $directory  = new EloquentEmployeeDirectory();
-        $reflection = new \ReflectionMethod(EloquentEmployeeDirectory::class, 'toDateTime');
-
-        // WHEN
-        /** @var \DateTimeInterface $result */
-        $result = $reflection->invoke($directory, '2024-01-15 14:30:00');
-
-        // THEN
-        expect($result)->toBeInstanceOf(\DateTimeInterface::class)
-            ->and($result->format('Y-m-d H:i:s'))->toBe('2024-01-15 14:30:00');
-    });
-
     it('returns null when employee is not found', function (): void {
         // GIVEN
         $directory  = new EloquentEmployeeDirectory();
diff --git a/tests/Integration/Infra/Providers/ConfigServiceProviderTest.php b/tests/Integration/Infra/Providers/ConfigServiceProviderTest.php
index 4bee6f9..1e9683b 100644
--- a/tests/Integration/Infra/Providers/ConfigServiceProviderTest.php
+++ b/tests/Integration/Infra/Providers/ConfigServiceProviderTest.php
@@ -10,6 +10,9 @@ use Application\Security\Config\HmacAuthConfig;
 use Application\Security\Config\SecurityAlertMailConfig;
 use Infra\Config\ArcadiaStorageConfig;
 use Infra\Providers\ConfigServiceProvider;
+use Psr\Clock\ClockInterface;
+use Shared\Time\Clock;
+use Shared\Time\SystemClock;
 use Tests\TestCase;
 
 uses(TestCase::class);
@@ -66,4 +69,15 @@ describe('ConfigServiceProvider Integration Tests', function (): void {
             ->and($config->cacheStore)->not->toBeEmpty()
             ->and($config->databaseConnection)->not->toBeEmpty();
     });
+
+    it('resolves PSR-20 ClockInterface and Clock service singleton configured with AppConfig timezone', function (): void {
+        // WHEN
+        $clock          = resolve(Clock::class);
+        $clockInterface = resolve(ClockInterface::class);
+
+        // THEN
+        expect($clock)->toBeInstanceOf(SystemClock::class)
+            ->and($clockInterface)->toBeInstanceOf(SystemClock::class)
+            ->and($clock->now()->getTimezone()->getName())->toBe('UTC');
+    });
 });
diff --git a/tests/Integration/Shared/Helpers/DateHelperTest.php b/tests/Integration/Shared/Helpers/DateHelperTest.php
index fb148c6..cefb089 100644
--- a/tests/Integration/Shared/Helpers/DateHelperTest.php
+++ b/tests/Integration/Shared/Helpers/DateHelperTest.php
@@ -28,13 +28,14 @@ describe('Date Helper Integration Tests', function (): void {
             ->toThrow(\ReflectionException::class);
     });
 
-    it('can parse various date formats', function (string $input, string $expectedFormat): void {
+    it('can parse various date formats and normalizes to UTC', function (string $input, string $expectedFormat): void {
         // GIVEN & WHEN
         $result = DatesHelper::parseDateTime($input);
 
         // THEN
         expect($result)->toBeInstanceOf(\DateTimeInterface::class)
-            ->and($result->format('Y-m-d'))->toBe($expectedFormat);
+            ->and($result->format('Y-m-d'))->toBe($expectedFormat)
+            ->and($result->getTimezone()->getName())->toBe('UTC');
     })->with([
         ['2025-12-25 12:10:23', '2025-12-25'],
         ['2025-12-25', '2025-12-25'],
@@ -45,6 +46,18 @@ describe('Date Helper Integration Tests', function (): void {
         ['2025/12/25', '2025-12-25'],
     ]);
 
+    it('converts non-UTC input timezone to exact UTC instant', function (): void {
+        // GIVEN
+        $inputWithOffset = '2025-12-25T14:10:23+02:00';
+
+        // WHEN
+        $result = DatesHelper::parseDateTime($inputWithOffset);
+
+        // THEN
+        expect($result->getTimezone()->getName())->toBe('UTC')
+            ->and($result->format('Y-m-d H:i:s'))->toBe('2025-12-25 12:10:23');
+    });
+
     it('throws InvalidDateFormatException for unparseable date strings', function (): void {
         // GIVEN
         $invalidDate = 'not-a-real-date-string';
@@ -63,7 +76,8 @@ describe('Date Helper Integration Tests', function (): void {
 
         // THEN
         expect($result)->toBeInstanceOf(\DateTimeInterface::class)
-            ->and($result->format('Y-m-d'))->toBe('2025-12-25');
+            ->and($result->format('Y-m-d'))->toBe('2025-12-25')
+            ->and($result->getTimezone()->getName())->toBe('UTC');
     });
 
     it('throws InvalidDateFormatException in parseFallback when fallback date is completely invalid logically', function (): void {
@@ -75,14 +89,14 @@ describe('Date Helper Integration Tests', function (): void {
             ->toThrow(InvalidDateFormatException::class, "Unrecognized date/time format: {$invalidFallbackDate}");
     });
 
-    it('handles isIn date boundary checks correctly', function (): void {
+    it('handles isIn date boundary checks correctly in UTC', function (): void {
         // GIVEN
-        $now = CarbonImmutable::create(2025, 6, 15, 12, 0, 0);
+        $now = CarbonImmutable::create(2025, 6, 15, 12, 0, 0, 'UTC');
         CarbonImmutable::setTestNow($now);
 
-        $past      = CarbonImmutable::create(2025, 1, 1);
-        $future    = CarbonImmutable::create(2025, 12, 31);
-        $farFuture = CarbonImmutable::create(2025, 12, 30);
+        $past      = CarbonImmutable::create(2025, 1, 1, 0, 0, 0, 'UTC');
+        $future    = CarbonImmutable::create(2025, 12, 31, 0, 0, 0, 'UTC');
+        $farFuture = CarbonImmutable::create(2025, 12, 30, 0, 0, 0, 'UTC');
 
         // WHEN & THEN
         expect(DatesHelper::isIn($past, $future))->toBeTrue()
@@ -94,16 +108,18 @@ describe('Date Helper Integration Tests', function (): void {
             ->and(DatesHelper::isIn(null, null))->toBeFalse();
     });
 
-    it('formats string or DateTimeInterface to RFC3339', function (): void {
+    it('formats string or DateTimeInterface to RFC3339 in UTC', function (): void {
         // GIVEN
-        $dateTimeObj = new \DateTimeImmutable('2025-12-25 12:10:23');
+        $dateTimeObj = new \DateTimeImmutable('2025-12-25 12:10:23', new \DateTimeZone('Europe/Paris'));
 
         // WHEN
         $resultFromObj = DatesHelper::toRfc3339($dateTimeObj);
         $resultFromStr = DatesHelper::toRfc3339('2025-12-25 12:10:23');
 
         // THEN
-        expect($resultFromObj)->toContain('2025-12-25T12:10:23')
-            ->and($resultFromStr)->toContain('2025-12-25T12:10:23');
+        expect($resultFromObj)->toBe('2025-12-25T11:10:23+00:00')
+            ->and($resultFromStr)->toBe('2025-12-25T12:10:23+00:00')
+            ->and(DatesHelper::toNullableRfc3339(null))->toBeNull()
+            ->and(DatesHelper::toNullableRfc3339($dateTimeObj))->toBe('2025-12-25T11:10:23+00:00');
     });
 });
diff --git a/tests/Unit/Infra/Adapters/Services/TimestampValidatorImplTest.php b/tests/Unit/Infra/Adapters/Services/TimestampValidatorImplTest.php
index 138c148..ed17d2e 100644
--- a/tests/Unit/Infra/Adapters/Services/TimestampValidatorImplTest.php
+++ b/tests/Unit/Infra/Adapters/Services/TimestampValidatorImplTest.php
@@ -4,18 +4,19 @@ declare(strict_types=1);
 
 namespace Tests\Unit\Infra\Adapters\Services;
 
-use DateTimeImmutable;
-use DateTimeZone;
 use Infra\Adapters\Services\TimestampValidatorImpl;
+use Shared\Time\FrozenClock;
 
 covers(TimestampValidatorImpl::class);
 
 describe('TimestampValidatorImpl Unit Tests', function (): void {
     it('accepts timestamps within the 300 seconds skew window', function (string $modifier): void {
         // GIVEN
-        $timezone  = new DateTimeZone('UTC');
-        $validator = new TimestampValidatorImpl($timezone);
-        $timestamp = new DateTimeImmutable($modifier, $timezone);
+        $timezone    = new \DateTimeZone('UTC');
+        $fixedTime   = new \DateTimeImmutable('2026-08-21 12:00:00', $timezone);
+        $frozenClock = new FrozenClock($fixedTime);
+        $validator   = new TimestampValidatorImpl($timezone, $frozenClock);
+        $timestamp   = $fixedTime->modify($modifier);
 
         // WHEN
         $isValid = $validator->validate($timestamp);
@@ -23,7 +24,7 @@ describe('TimestampValidatorImpl Unit Tests', function (): void {
         // THEN
         expect($isValid)->toBeTrue();
     })->with([
-        'now',
+        '0 seconds',
         '-2 minutes',
         '+2 minutes',
         '-299 seconds',
@@ -32,9 +33,11 @@ describe('TimestampValidatorImpl Unit Tests', function (): void {
 
     it('rejects timestamps outside the 300 seconds skew window', function (string $modifier): void {
         // GIVEN
-        $timezone  = new DateTimeZone('UTC');
-        $validator = new TimestampValidatorImpl($timezone);
-        $timestamp = new DateTimeImmutable($modifier, $timezone);
+        $timezone    = new \DateTimeZone('UTC');
+        $fixedTime   = new \DateTimeImmutable('2026-08-21 12:00:00', $timezone);
+        $frozenClock = new FrozenClock($fixedTime);
+        $validator   = new TimestampValidatorImpl($timezone, $frozenClock);
+        $timestamp   = $fixedTime->modify($modifier);
 
         // WHEN
         $isValid = $validator->validate($timestamp);
diff --git a/tests/Unit/Infra/Casts/UtcDateTimeCastTest.php b/tests/Unit/Infra/Casts/UtcDateTimeCastTest.php
new file mode 100644
index 0000000..88be180
--- /dev/null
+++ b/tests/Unit/Infra/Casts/UtcDateTimeCastTest.php
@@ -0,0 +1,112 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tests\Unit\Infra\Casts;
+
+use Illuminate\Database\Eloquent\Model;
+use Infra\Casts\UtcDateTimeCast;
+
+covers(UtcDateTimeCast::class);
+
+describe('UtcDateTimeCast Unit Tests', function (): void {
+    it('casts database string to UTC DateTimeImmutable', function (): void {
+        // GIVEN
+        $cast  = new UtcDateTimeCast();
+        $model = new class () extends Model
+        {
+        };
+
+        // WHEN
+        $result = $cast->get($model, 'created_at', '2026-08-21 14:30:00', []);
+
+        // THEN
+        expect($result)->toBeInstanceOf(\DateTimeImmutable::class)
+            ->and($result?->getTimezone()->getName())->toBe('UTC')
+            ->and($result?->format('Y-m-d H:i:s'))->toBe('2026-08-21 14:30:00');
+    });
+
+    it('casts non-UTC DateTimeInterface to UTC DateTimeImmutable upon get', function (): void {
+        // GIVEN
+        $cast        = new UtcDateTimeCast();
+        $model       = new class () extends Model
+        {
+        };
+        $parisDate   = new \DateTimeImmutable('2026-08-21 16:30:00', new \DateTimeZone('Europe/Paris'));
+
+        // WHEN
+        $result = $cast->get($model, 'created_at', $parisDate, []);
+
+        // THEN
+        expect($result)->toBeInstanceOf(\DateTimeImmutable::class)
+            ->and($result?->getTimezone()->getName())->toBe('UTC')
+            ->and($result?->format('Y-m-d H:i:s'))->toBe('2026-08-21 14:30:00');
+    });
+
+    it('handles null and empty string upon get', function (): void {
+        // GIVEN
+        $cast  = new UtcDateTimeCast();
+        $model = new class () extends Model
+        {
+        };
+
+        // WHEN & THEN
+        expect($cast->get($model, 'created_at', null, []))->toBeNull()
+            ->and($cast->get($model, 'created_at', '', []))->toBeNull()
+            ->and($cast->get($model, 'created_at', '   ', []))->toBeNull();
+    });
+
+    it('sets DateTimeInterface to UTC string format for database storage', function (): void {
+        // GIVEN
+        $cast      = new UtcDateTimeCast();
+        $model     = new class () extends Model
+        {
+        };
+        $parisDate = new \DateTimeImmutable('2026-08-21 16:30:00', new \DateTimeZone('Europe/Paris'));
+
+        // WHEN
+        $result = $cast->set($model, 'created_at', $parisDate, []);
+
+        // THEN
+        expect($result)->toBe('2026-08-21 14:30:00');
+    });
+
+    it('sets string date to UTC string format for database storage', function (): void {
+        // GIVEN
+        $cast  = new UtcDateTimeCast();
+        $model = new class () extends Model
+        {
+        };
+
+        // WHEN
+        $result = $cast->set($model, 'created_at', '2026-08-21T16:30:00+02:00', []);
+
+        // THEN
+        expect($result)->toBe('2026-08-21 14:30:00');
+    });
+
+    it('handles null and empty string upon set', function (): void {
+        // GIVEN
+        $cast  = new UtcDateTimeCast();
+        $model = new class () extends Model
+        {
+        };
+
+        // WHEN & THEN
+        expect($cast->set($model, 'created_at', null, []))->toBeNull()
+            ->and($cast->set($model, 'created_at', '', []))->toBeNull()
+            ->and($cast->set($model, 'created_at', '   ', []))->toBeNull();
+    });
+
+    it('throws InvalidArgumentException when setting unsupported type', function (): void {
+        // GIVEN
+        $cast  = new UtcDateTimeCast();
+        $model = new class () extends Model
+        {
+        };
+
+        // WHEN & THEN
+        expect(fn () => $cast->set($model, 'created_at', 12345, []))
+            ->toThrow(\InvalidArgumentException::class, 'Cannot cast value of type int to UTC datetime');
+    });
+});
diff --git a/tests/Unit/Presentation/Api/V1/Dto/Brands/BrandDtoTest.php b/tests/Unit/Presentation/Api/V1/Dto/Brands/BrandDtoTest.php
index bbc48a2..e39cd2a 100644
--- a/tests/Unit/Presentation/Api/V1/Dto/Brands/BrandDtoTest.php
+++ b/tests/Unit/Presentation/Api/V1/Dto/Brands/BrandDtoTest.php
@@ -12,6 +12,7 @@ use Domain\Models\ValueObjects\Brand\BrandName;
 use Presentation\Api\V1\Dto\Brands\BrandDto;
 use Presentation\Api\V1\Presenters\Brands\BrandShowView;
 use Ramsey\Uuid\Uuid;
+use Shared\Helpers\DatesHelper;
 
 covers(BrandDto::class);
 
@@ -40,13 +41,13 @@ describe('BrandDto Unit Tests', function (): void {
             ->and($dto->name)->toBe('Le Gaulois')
             ->and($dto->code)->toBe('LGL01')
             ->and($dto->arcadiaId)->toBe(1)
-            ->and($dto->createdAt)->toBe($createdAt->format(\DateTimeInterface::ATOM))
+            ->and($dto->createdAt)->toBe(DatesHelper::toRfc3339($createdAt))
             ->and($dto->toArray())->toBe([
                 'id'        => (string) $id,
                 'code'      => 'LGL01',
                 'name'      => 'Le Gaulois',
                 'arcadiaId' => 1,
-                'createdAt' => $createdAt->format(\DateTimeInterface::ATOM),
+                'createdAt' => DatesHelper::toRfc3339($createdAt),
             ]);
     });
 
diff --git a/tests/Unit/Presentation/Console/Presenters/Brands/ListBrandsPresenterTest.php b/tests/Unit/Presentation/Console/Presenters/Brands/ListBrandsPresenterTest.php
index 73e0af0..329f9a2 100644
--- a/tests/Unit/Presentation/Console/Presenters/Brands/ListBrandsPresenterTest.php
+++ b/tests/Unit/Presentation/Console/Presenters/Brands/ListBrandsPresenterTest.php
@@ -50,7 +50,7 @@ describe('ListBrandsPresenter Unit Tests', function (): void {
             ->and($view->rows[0]->code)->toBe('LGL01')
             ->and($view->rows[0]->name)->toBe('Le Gaulois')
             ->and($view->rows[0]->arcadiaId)->toBe(1)
-            ->and($view->rows[0]->createdAt)->toBe('2024-01-15 08:00:00');
+            ->and($view->rows[0]->createdAt)->toBe('2024-01-15T08:00:00+00:00');
     });
 
     it('returns empty view when no brands in output', function (): void {
diff --git a/tests/Unit/Presentation/Console/Presenters/Clients/ListClientsPresenterTest.php b/tests/Unit/Presentation/Console/Presenters/Clients/ListClientsPresenterTest.php
index 5920f91..0ae2639 100644
--- a/tests/Unit/Presentation/Console/Presenters/Clients/ListClientsPresenterTest.php
+++ b/tests/Unit/Presentation/Console/Presenters/Clients/ListClientsPresenterTest.php
@@ -60,7 +60,7 @@ describe('ListClientsPresenter Unit Tests', function (): void {
             ->and($view->rows[0]->name)->toBe('Client 1')
             ->and($view->rows[0]->identifier)->toBe($identifier->value)
             ->and($view->rows[0]->status)->toBe('Active')
-            ->and($view->rows[0]->lastUpdatedAt)->toBe('2024-01-15 10:30:00');
+            ->and($view->rows[0]->lastUpdatedAt)->toBe('2024-01-15T10:30:00+00:00');
     });
 
     it('handles inactive client status and calculates total pages correctly', function (): void {
diff --git a/tests/Unit/Shared/Helpers/UuidHelperTest.php b/tests/Unit/Shared/Helpers/UuidHelperTest.php
index 8728e41..4e4d3ad 100644
--- a/tests/Unit/Shared/Helpers/UuidHelperTest.php
+++ b/tests/Unit/Shared/Helpers/UuidHelperTest.php
@@ -117,6 +117,7 @@ describe('Uuid Helper Unit Tests', function (): void {
 
         // THEN
         expect($dateTime)->toBeInstanceOf(\DateTimeImmutable::class)
+            ->and($dateTime->getTimezone()->getName())->toBe('UTC')
             ->and($dateTime->getTimestamp())->toBeLessThanOrEqual(time())
             ->and($dateTime->getTimestamp())->toBeGreaterThan(1700000000);
     });
diff --git a/tests/Unit/Shared/Time/ClockTest.php b/tests/Unit/Shared/Time/ClockTest.php
new file mode 100644
index 0000000..879eace
--- /dev/null
+++ b/tests/Unit/Shared/Time/ClockTest.php
@@ -0,0 +1,96 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tests\Unit\Shared\Time;
+
+use Psr\Clock\ClockInterface;
+use Shared\Time\Clock;
+use Shared\Time\FrozenClock;
+use Shared\Time\SystemClock;
+use Shared\Time\SystemUtcClock;
+use Shared\Time\Utc;
+
+covers(
+    SystemClock::class,
+    SystemUtcClock::class,
+    FrozenClock::class,
+    Utc::class,
+);
+
+afterEach(function (): void {
+    Utc::restore();
+});
+
+describe('PSR-20 UTC Clock Unit Tests', function (): void {
+    it('implements Psr ClockInterface and Clock contract with configured timezone', function (): void {
+        // GIVEN
+        $parisClock = new SystemClock(new \DateTimeZone('Europe/Paris'));
+        $utcClock   = new SystemUtcClock();
+
+        // WHEN
+        $parisNow = $parisClock->now();
+        $utcNow   = $utcClock->now();
+
+        // THEN
+        expect($parisClock)->toBeInstanceOf(ClockInterface::class)
+            ->and($parisClock)->toBeInstanceOf(Clock::class)
+            ->and($parisNow->getTimezone()->getName())->toBe('Europe/Paris')
+            ->and($parisClock->timezone()->getName())->toBe('Europe/Paris')
+            ->and($utcNow->getTimezone()->getName())->toBe('UTC');
+    });
+
+    it('parses date strings and normalizes to UTC with SystemUtcClock', function (): void {
+        // GIVEN
+        $clock = new SystemUtcClock();
+
+        // WHEN
+        $utcTime    = $clock->parse('2026-08-21T15:00:00+02:00');
+        $startOfDay = $clock->startOfDay('2026-08-21');
+        $endOfDay   = $clock->endOfDay('2026-08-21');
+        $isoString  = $clock->toIso8601($utcTime);
+
+        // THEN
+        expect($utcTime->getTimezone()->getName())->toBe('UTC')
+            ->and($utcTime->format('Y-m-d H:i:s'))->toBe('2026-08-21 13:00:00')
+            ->and($startOfDay->format('Y-m-d H:i:s'))->toBe('2026-08-21 00:00:00')
+            ->and($endOfDay->format('Y-m-d H:i:s.u'))->toBe('2026-08-21 23:59:59.999999')
+            ->and($isoString)->toBe('2026-08-21T13:00:00+00:00');
+    });
+
+    it('allows freezing and manipulating time with FrozenClock', function (): void {
+        // GIVEN
+        $fixedTime   = new \DateTimeImmutable('2026-08-21 10:00:00', new \DateTimeZone('UTC'));
+        $frozenClock = new FrozenClock($fixedTime);
+
+        // THEN
+        expect($frozenClock->now()->format('Y-m-d H:i:s'))->toBe('2026-08-21 10:00:00');
+
+        // WHEN
+        $frozenClock->setTo('2026-12-31 23:59:59');
+
+        // THEN
+        expect($frozenClock->now()->format('Y-m-d H:i:s'))->toBe('2026-12-31 23:59:59')
+            ->and($frozenClock->now()->getTimezone()->getName())->toBe('UTC');
+    });
+
+    it('provides centralized static access through Utc facade', function (): void {
+        // GIVEN
+        $frozen = Utc::freeze(new \DateTimeImmutable('2026-08-21 14:00:00', new \DateTimeZone('UTC')));
+
+        // THEN
+        expect(Utc::now()->format('Y-m-d H:i:s'))->toBe('2026-08-21 14:00:00')
+            ->and(Utc::parse('2026-08-21 12:00:00')->format('Y-m-d H:i:s'))->toBe('2026-08-21 12:00:00')
+            ->and(Utc::startOfDay('2026-08-21')->format('Y-m-d H:i:s'))->toBe('2026-08-21 00:00:00')
+            ->and(Utc::endOfDay('2026-08-21')->format('Y-m-d H:i:s'))->toBe('2026-08-21 23:59:59')
+            ->and(Utc::toRfc3339('2026-08-21 14:00:00'))->toBe('2026-08-21T14:00:00+00:00')
+            ->and(Utc::toNullableRfc3339(null))->toBeNull()
+            ->and(Utc::toNullableRfc3339('2026-08-21 14:00:00'))->toBe('2026-08-21T14:00:00+00:00');
+
+        // WHEN
+        Utc::restore();
+
+        // THEN
+        expect(Utc::getClock())->toBeInstanceOf(SystemUtcClock::class);
+    });
+});