Fix DST transition issue causing forced caching of non-cacheable responses

src/Strategy/PrivateCacheStrategy.php

@@ -83,7 +83,7 @@ protected function getCacheObject(RequestInterface $request, ResponseInterface $
 
         if ($cacheControl->has('no-cache')) {
             // Stale response see RFC7234 section 5.2.1.4
-            $entry = new CacheEntry($request, $response, new \DateTime('-1 seconds'));
+            $entry = new CacheEntry($request, $response, new \DateTime('@' . (time() - 1)));
 
             return $entry->hasValidationInformation() ? $entry : null;
         }
@@ -109,7 +109,7 @@ protected function getCacheObject(RequestInterface $request, ResponseInterface $
             }
         }
 
-        return new CacheEntry($request, $response, new \DateTime('-1 seconds'));
+        return new CacheEntry($request, $response, new \DateTime('@' . (time() - 1)));
     }
 
     /**

tests/DstTransitionTest.php

@@ -0,0 +1,75 @@
+<?php
+
+namespace Kevinrob\GuzzleCache\Tests;
+
+use Kevinrob\GuzzleCache\CacheEntry;
+use GuzzleHttp\Psr7\Request;
+use GuzzleHttp\Psr7\Response;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * Test for DST transition issue where DateTime('-1 seconds') can create
+ * future timestamps during timezone transitions.
+ * 
+ * This test verifies the fix for issue #194.
+ */
+class DstTransitionTest extends TestCase
+{
+    private $originalTimezone;
+
+    protected function setUp(): void
+    {
+        // Save original timezone
+        $this->originalTimezone = date_default_timezone_get();
+    }
+
+    protected function tearDown(): void
+    {
+        // Restore original timezone
+        date_default_timezone_set($this->originalTimezone);
+    }
+
+    /**
+     * Test CacheEntry behavior with UTC timestamp approach
+     * This ensures that cache entries marked for immediate expiry
+     * behave consistently across timezones.
+     */
+    public function testCacheEntryWithUtcTimestampIsAlwaysStale()
+    {
+        $timezones = ['UTC', 'Europe/Berlin', 'America/New_York'];
+
+        foreach ($timezones as $timezone) {
+            date_default_timezone_set($timezone);
+
+            $request = new Request('GET', 'http://example.com');
+            $response = new Response(200, [], 'test content');
+
+            // Create entry with UTC timestamp approach (the fix)
+            $entry = new CacheEntry($request, $response, new \DateTime('@' . (time() - 1)));
+
+            // Should always be stale regardless of timezone
+            $this->assertTrue($entry->isStale(), "Entry should be stale in timezone: $timezone");
+            $this->assertFalse($entry->isFresh(), "Entry should not be fresh in timezone: $timezone");
+            $this->assertGreaterThan(0, $entry->getStaleAge(), "Stale age should be positive in timezone: $timezone");
+        }
+    }
+
+    /**
+     * Test that validates the TTL calculation is correct
+     */
+    public function testCacheEntryTtlWithUtcTimestamp()
+    {
+        date_default_timezone_set('Europe/Berlin');
+
+        $request = new Request('GET', 'http://example.com');
+        $response = new Response(200, [], 'test content');
+
+        // Create entry with UTC timestamp approach
+        $entry = new CacheEntry($request, $response, new \DateTime('@' . (time() - 1)));
+
+        $ttl = $entry->getTTL();
+
+        // TTL should be -1 for expired entries without validation info
+        $this->assertEquals(-1, $ttl, "TTL should be -1 for expired entries without validation info");
+    }
+}