[RateLimiter] Fix DateInterval normalization

RateLimiterFactory.php

@@ -69,7 +69,11 @@ protected static function configureOptions(OptionsResolver $options): void
     {
         $intervalNormalizer = static function (Options $options, string $interval): \DateInterval {
             try {
-                return (new \DateTimeImmutable())->diff(new \DateTimeImmutable('+'.$interval));
+                // Create DateTimeImmutable from unix timesatmp, so the default timezone is ignored and we don't need to
+                // deal with quirks happening when modifying dates using a timezone with DST.
+                $now = \DateTimeImmutable::createFromFormat('U', time());
+
+                return $now->diff($now->modify('+'.$interval));
             } catch (\Exception $e) {
                 if (!preg_match('/Failed to parse time string \(\+([^)]+)\)/', $e->getMessage(), $m)) {
                     throw $e;

Tests/RateLimiterFactoryTest.php

@@ -12,6 +12,7 @@
 namespace Symfony\Component\RateLimiter\Tests;
 
 use PHPUnit\Framework\TestCase;
+use Symfony\Bridge\PhpUnit\ClockMock;
 use Symfony\Component\OptionsResolver\Exception\MissingOptionsException;
 use Symfony\Component\RateLimiter\Policy\FixedWindowLimiter;
 use Symfony\Component\RateLimiter\Policy\NoLimiter;
@@ -76,4 +77,37 @@ public static function invalidConfigProvider()
             'policy' => 'token_bucket',
         ]];
     }
+
+    /**
+     * @group time-sensitive
+     */
+    public function testExpirationTimeCalculationWhenUsingDefaultTimezoneRomeWithIntervalAfterCETChange()
+    {
+        $originalTimezone = date_default_timezone_get();
+        try {
+            // Timestamp for 'Sun 27 Oct 2024 12:59:40 AM UTC' that's just 20 seconds before switch CEST->CET
+            ClockMock::withClockMock(1729990780);
+
+            // This is a prerequisite for the bug to happen
+            date_default_timezone_set('Europe/Rome');
+
+            $storage = new InMemoryStorage();
+            $factory = new RateLimiterFactory(
+                [
+                    'id' => 'id_1',
+                    'policy' => 'fixed_window',
+                    'limit' => 30,
+                    'interval' => '21 seconds',
+                ],
+                $storage
+            );
+            $rateLimiter = $factory->create('key');
+            $rateLimiter->consume(1);
+            $limiterState = $storage->fetch('id_1-key');
+            // As expected the expiration is equal to the interval we defined
+            $this->assertSame(21, $limiterState->getExpirationTime());
+        } finally {
+            date_default_timezone_set($originalTimezone);
+        }
+    }
 }

Util/TimeUtil.php

@@ -20,7 +20,7 @@ final class TimeUtil
 {
     public static function dateIntervalToSeconds(\DateInterval $interval): int
     {
-        $now = new \DateTimeImmutable();
+        $now = \DateTimeImmutable::createFromFormat('U', time());
 
         return $now->add($interval)->getTimestamp() - $now->getTimestamp();
     }