diff --git a/src/Io/Clock.php b/src/Io/Clock.php
new file mode 100644
index 00000000..92c1cb09
--- /dev/null
+++ b/src/Io/Clock.php
@@ -0,0 +1,54 @@
+<?php
+
+namespace React\Http\Io;
+
+use React\EventLoop\LoopInterface;
+
+/**
+ * [internal] Clock source that returns current timestamp and memoize clock for same tick
+ *
+ * This is mostly used as an internal optimization to avoid unneeded syscalls to
+ * get the current system time multiple times within the same loop tick. For the
+ * purpose of the HTTP server, the clock is assumed to not change to a
+ * significant degree within the same loop tick. If you need a high precision
+ * clock source, you may want to use `\hrtime()` instead (PHP 7.3+).
+ *
+ * The API is modelled to resemble the PSR-20 `ClockInterface` (in draft at the
+ * time of writing this), but uses a `float` return value for performance
+ * reasons instead.
+ *
+ * Note that this is an internal class only and nothing you should usually care
+ * about for outside use.
+ *
+ * @internal
+ */
+class Clock
+{
+    /** @var LoopInterface $loop */
+    private $loop;
+
+    /** @var ?float */
+    private $now;
+
+    public function __construct(LoopInterface $loop)
+    {
+        $this->loop = $loop;
+    }
+
+    /** @return float */
+    public function now()
+    {
+        if ($this->now === null) {
+            $this->now = \microtime(true);
+
+            // remember clock for current loop tick only and update on next tick
+            $now =& $this->now;
+            $this->loop->futureTick(function () use (&$now) {
+                assert($now !== null);
+                $now = null;
+            });
+        }
+
+        return $this->now;
+    }
+}
diff --git a/src/Io/RequestHeaderParser.php b/src/Io/RequestHeaderParser.php
index e5554c46..6930afaf 100644
--- a/src/Io/RequestHeaderParser.php
+++ b/src/Io/RequestHeaderParser.php
@@ -24,6 +24,14 @@ class RequestHeaderParser extends EventEmitter
 {
     private $maxSize = 8192;
 
+    /** @var Clock */
+    private $clock;
+
+    public function __construct(Clock $clock)
+    {
+        $this->clock = $clock;
+    }
+
     public function handle(ConnectionInterface $conn)
     {
         $buffer = '';
@@ -155,8 +163,8 @@ public function parseRequest($headers, $remoteSocketUri, $localSocketUri)
         // create new obj implementing ServerRequestInterface by preserving all
         // previous properties and restoring original request-target
         $serverParams = array(
-            'REQUEST_TIME' => \time(),
-            'REQUEST_TIME_FLOAT' => \microtime(true)
+            'REQUEST_TIME' => (int) ($now = $this->clock->now()),
+            'REQUEST_TIME_FLOAT' => $now
         );
 
         // scheme is `http` unless TLS is used
diff --git a/src/Io/StreamingServer.php b/src/Io/StreamingServer.php
index d73d527d..a054be3d 100644
--- a/src/Io/StreamingServer.php
+++ b/src/Io/StreamingServer.php
@@ -84,7 +84,9 @@ final class StreamingServer extends EventEmitter
 {
     private $callback;
     private $parser;
-    private $loop;
+
+    /** @var Clock */
+    private $clock;
 
     /**
      * Creates an HTTP server that invokes the given callback for each incoming HTTP request
@@ -104,10 +106,9 @@ public function __construct(LoopInterface $loop, $requestHandler)
             throw new \InvalidArgumentException('Invalid request handler given');
         }
 
-        $this->loop = $loop;
-
         $this->callback = $requestHandler;
-        $this->parser = new RequestHeaderParser();
+        $this->clock = new Clock($loop);
+        $this->parser = new RequestHeaderParser($this->clock);
 
         $that = $this;
         $this->parser->on('headers', function (ServerRequestInterface $request, ConnectionInterface $conn) use ($that) {
@@ -255,7 +256,7 @@ public function handleResponse(ConnectionInterface $connection, ServerRequestInt
         // assign default "Date" header from current time automatically
         if (!$response->hasHeader('Date')) {
             // IMF-fixdate  = day-name "," SP date1 SP time-of-day SP GMT
-            $response = $response->withHeader('Date', gmdate('D, d M Y H:i:s') . ' GMT');
+            $response = $response->withHeader('Date', gmdate('D, d M Y H:i:s', (int) $this->clock->now()) . ' GMT');
         } elseif ($response->getHeaderLine('Date') === ''){
             $response = $response->withoutHeader('Date');
         }
diff --git a/tests/HttpServerTest.php b/tests/HttpServerTest.php
index a6d8057b..4d00fcef 100644
--- a/tests/HttpServerTest.php
+++ b/tests/HttpServerTest.php
@@ -54,9 +54,13 @@ public function testConstructWithoutLoopAssignsLoopAutomatically()
         $ref->setAccessible(true);
         $streamingServer = $ref->getValue($http);
 
-        $ref = new \ReflectionProperty($streamingServer, 'loop');
+        $ref = new \ReflectionProperty($streamingServer, 'clock');
         $ref->setAccessible(true);
-        $loop = $ref->getValue($streamingServer);
+        $clock = $ref->getValue($streamingServer);
+
+        $ref = new \ReflectionProperty($clock, 'loop');
+        $ref->setAccessible(true);
+        $loop = $ref->getValue($clock);
 
         $this->assertInstanceOf('React\EventLoop\LoopInterface', $loop);
     }
diff --git a/tests/Io/ClockTest.php b/tests/Io/ClockTest.php
new file mode 100644
index 00000000..8f4b90fa
--- /dev/null
+++ b/tests/Io/ClockTest.php
@@ -0,0 +1,43 @@
+<?php
+
+namespace React\Tests\Http\Io;
+
+use PHPUnit\Framework\TestCase;
+use React\Http\Io\Clock;
+
+class ClockTest extends TestCase
+{
+    public function testNowReturnsSameTimestampMultipleTimesInSameTick()
+    {
+        $loop = $this->getMockBuilder('React\EventLoop\LoopInterface')->getMock();
+
+        $clock = new Clock($loop);
+
+        $now = $clock->now();
+        $this->assertTrue(is_float($now)); // assertIsFloat() on PHPUnit 8+
+        $this->assertEquals($now, $clock->now());
+    }
+
+    public function testNowResetsMemoizedTimestampOnFutureTick()
+    {
+        $tick = null;
+        $loop = $this->getMockBuilder('React\EventLoop\LoopInterface')->getMock();
+        $loop->expects($this->once())->method('futureTick')->with($this->callback(function ($cb) use (&$tick) {
+            $tick = $cb;
+            return true;
+        }));
+
+        $clock = new Clock($loop);
+
+        $now = $clock->now();
+
+        $ref = new \ReflectionProperty($clock, 'now');
+        $ref->setAccessible(true);
+        $this->assertEquals($now, $ref->getValue($clock));
+
+        $this->assertNotNull($tick);
+        $tick();
+
+        $this->assertNull($ref->getValue($clock));
+    }
+}
diff --git a/tests/Io/RequestHeaderParserTest.php b/tests/Io/RequestHeaderParserTest.php
index 356443fb..7ba7fe01 100644
--- a/tests/Io/RequestHeaderParserTest.php
+++ b/tests/Io/RequestHeaderParserTest.php
@@ -10,7 +10,9 @@ class RequestHeaderParserTest extends TestCase
 {
     public function testSplitShouldHappenOnDoubleCrlf()
     {
-        $parser = new RequestHeaderParser();
+        $clock = $this->getMockBuilder('React\Http\Io\Clock')->disableOriginalConstructor()->getMock();
+
+        $parser = new RequestHeaderParser($clock);
         $parser->on('headers', $this->expectCallableNever());
 
         $connection = $this->getMockBuilder('React\Socket\Connection')->disableOriginalConstructor()->setMethods(null)->getMock();
@@ -29,7 +31,9 @@ public function testSplitShouldHappenOnDoubleCrlf()
 
     public function testFeedInOneGo()
     {
-        $parser = new RequestHeaderParser();
+        $clock = $this->getMockBuilder('React\Http\Io\Clock')->disableOriginalConstructor()->getMock();
+
+        $parser = new RequestHeaderParser($clock);
         $parser->on('headers', $this->expectCallableOnce());
 
         $connection = $this->getMockBuilder('React\Socket\Connection')->disableOriginalConstructor()->setMethods(null)->getMock();
@@ -41,7 +45,9 @@ public function testFeedInOneGo()
 
     public function testFeedTwoRequestsOnSeparateConnections()
     {
-        $parser = new RequestHeaderParser();
+        $clock = $this->getMockBuilder('React\Http\Io\Clock')->disableOriginalConstructor()->getMock();
+
+        $parser = new RequestHeaderParser($clock);
 
         $called = 0;
         $parser->on('headers', function () use (&$called) {
@@ -65,7 +71,9 @@ public function testHeadersEventShouldEmitRequestAndConnection()
         $request = null;
         $conn = null;
 
-        $parser = new RequestHeaderParser();
+        $clock = $this->getMockBuilder('React\Http\Io\Clock')->disableOriginalConstructor()->getMock();
+
+        $parser = new RequestHeaderParser($clock);
         $parser->on('headers', function ($parsedRequest, $connection) use (&$request, &$conn) {
             $request = $parsedRequest;
             $conn = $connection;
@@ -88,7 +96,9 @@ public function testHeadersEventShouldEmitRequestAndConnection()
 
     public function testHeadersEventShouldEmitRequestWhichShouldEmitEndForStreamingBodyWithoutContentLengthFromInitialRequestBody()
     {
-        $parser = new RequestHeaderParser();
+        $clock = $this->getMockBuilder('React\Http\Io\Clock')->disableOriginalConstructor()->getMock();
+
+        $parser = new RequestHeaderParser($clock);
 
         $ended = false;
         $that = $this;
@@ -112,7 +122,9 @@ public function testHeadersEventShouldEmitRequestWhichShouldEmitEndForStreamingB
 
     public function testHeadersEventShouldEmitRequestWhichShouldEmitStreamingBodyDataFromInitialRequestBody()
     {
-        $parser = new RequestHeaderParser();
+        $clock = $this->getMockBuilder('React\Http\Io\Clock')->disableOriginalConstructor()->getMock();
+
+        $parser = new RequestHeaderParser($clock);
 
         $buffer = '';
         $that = $this;
@@ -140,7 +152,9 @@ public function testHeadersEventShouldEmitRequestWhichShouldEmitStreamingBodyDat
 
     public function testHeadersEventShouldEmitRequestWhichShouldEmitStreamingBodyWithPlentyOfDataFromInitialRequestBody()
     {
-        $parser = new RequestHeaderParser();
+        $clock = $this->getMockBuilder('React\Http\Io\Clock')->disableOriginalConstructor()->getMock();
+
+        $parser = new RequestHeaderParser($clock);
 
         $buffer = '';
         $that = $this;
@@ -166,7 +180,9 @@ public function testHeadersEventShouldEmitRequestWhichShouldEmitStreamingBodyWit
 
     public function testHeadersEventShouldEmitRequestWhichShouldNotEmitStreamingBodyDataWithoutContentLengthFromInitialRequestBody()
     {
-        $parser = new RequestHeaderParser();
+        $clock = $this->getMockBuilder('React\Http\Io\Clock')->disableOriginalConstructor()->getMock();
+
+        $parser = new RequestHeaderParser($clock);
 
         $buffer = '';
         $that = $this;
@@ -191,7 +207,9 @@ public function testHeadersEventShouldEmitRequestWhichShouldNotEmitStreamingBody
 
     public function testHeadersEventShouldEmitRequestWhichShouldEmitStreamingBodyDataUntilContentLengthBoundaryFromInitialRequestBody()
     {
-        $parser = new RequestHeaderParser();
+        $clock = $this->getMockBuilder('React\Http\Io\Clock')->disableOriginalConstructor()->getMock();
+
+        $parser = new RequestHeaderParser($clock);
 
         $buffer = '';
         $that = $this;
@@ -218,7 +236,9 @@ public function testHeadersEventShouldParsePathAndQueryString()
     {
         $request = null;
 
-        $parser = new RequestHeaderParser();
+        $clock = $this->getMockBuilder('React\Http\Io\Clock')->disableOriginalConstructor()->getMock();
+
+        $parser = new RequestHeaderParser($clock);
         $parser->on('headers', function ($parsedRequest) use (&$request) {
             $request = $parsedRequest;
         });
@@ -245,7 +265,9 @@ public function testHeaderEventWithShouldApplyDefaultAddressFromLocalConnectionA
     {
         $request = null;
 
-        $parser = new RequestHeaderParser();
+        $clock = $this->getMockBuilder('React\Http\Io\Clock')->disableOriginalConstructor()->getMock();
+
+        $parser = new RequestHeaderParser($clock);
         $parser->on('headers', function ($parsedRequest) use (&$request) {
             $request = $parsedRequest;
         });
@@ -264,7 +286,9 @@ public function testHeaderEventViaHttpsShouldApplyHttpsSchemeFromLocalTlsConnect
     {
         $request = null;
 
-        $parser = new RequestHeaderParser();
+        $clock = $this->getMockBuilder('React\Http\Io\Clock')->disableOriginalConstructor()->getMock();
+
+        $parser = new RequestHeaderParser($clock);
         $parser->on('headers', function ($parsedRequest) use (&$request) {
             $request = $parsedRequest;
         });
@@ -284,7 +308,9 @@ public function testHeaderOverflowShouldEmitError()
         $error = null;
         $passedConnection = null;
 
-        $parser = new RequestHeaderParser();
+        $clock = $this->getMockBuilder('React\Http\Io\Clock')->disableOriginalConstructor()->getMock();
+
+        $parser = new RequestHeaderParser($clock);
         $parser->on('headers', $this->expectCallableNever());
         $parser->on('error', function ($message, $connection) use (&$error, &$passedConnection) {
             $error = $message;
@@ -306,7 +332,9 @@ public function testInvalidEmptyRequestHeadersParseException()
     {
         $error = null;
 
-        $parser = new RequestHeaderParser();
+        $clock = $this->getMockBuilder('React\Http\Io\Clock')->disableOriginalConstructor()->getMock();
+
+        $parser = new RequestHeaderParser($clock);
         $parser->on('headers', $this->expectCallableNever());
         $parser->on('error', function ($message) use (&$error) {
             $error = $message;
@@ -325,7 +353,9 @@ public function testInvalidMalformedRequestLineParseException()
     {
         $error = null;
 
-        $parser = new RequestHeaderParser();
+        $clock = $this->getMockBuilder('React\Http\Io\Clock')->disableOriginalConstructor()->getMock();
+
+        $parser = new RequestHeaderParser($clock);
         $parser->on('headers', $this->expectCallableNever());
         $parser->on('error', function ($message) use (&$error) {
             $error = $message;
@@ -344,7 +374,9 @@ public function testInvalidMalformedRequestHeadersThrowsParseException()
     {
         $error = null;
 
-        $parser = new RequestHeaderParser();
+        $clock = $this->getMockBuilder('React\Http\Io\Clock')->disableOriginalConstructor()->getMock();
+
+        $parser = new RequestHeaderParser($clock);
         $parser->on('headers', $this->expectCallableNever());
         $parser->on('error', function ($message) use (&$error) {
             $error = $message;
@@ -363,7 +395,9 @@ public function testInvalidMalformedRequestHeadersWhitespaceThrowsParseException
     {
         $error = null;
 
-        $parser = new RequestHeaderParser();
+        $clock = $this->getMockBuilder('React\Http\Io\Clock')->disableOriginalConstructor()->getMock();
+
+        $parser = new RequestHeaderParser($clock);
         $parser->on('headers', $this->expectCallableNever());
         $parser->on('error', function ($message) use (&$error) {
             $error = $message;
@@ -382,7 +416,9 @@ public function testInvalidAbsoluteFormSchemeEmitsError()
     {
         $error = null;
 
-        $parser = new RequestHeaderParser();
+        $clock = $this->getMockBuilder('React\Http\Io\Clock')->disableOriginalConstructor()->getMock();
+
+        $parser = new RequestHeaderParser($clock);
         $parser->on('headers', $this->expectCallableNever());
         $parser->on('error', function ($message) use (&$error) {
             $error = $message;
@@ -401,7 +437,9 @@ public function testOriginFormWithSchemeSeparatorInParam()
     {
         $request = null;
 
-        $parser = new RequestHeaderParser();
+        $clock = $this->getMockBuilder('React\Http\Io\Clock')->disableOriginalConstructor()->getMock();
+
+        $parser = new RequestHeaderParser($clock);
         $parser->on('error', $this->expectCallableNever());
         $parser->on('headers', function ($parsedRequest, $parsedBodyBuffer) use (&$request) {
             $request = $parsedRequest;
@@ -426,7 +464,9 @@ public function testUriStartingWithColonSlashSlashFails()
     {
         $error = null;
 
-        $parser = new RequestHeaderParser();
+        $clock = $this->getMockBuilder('React\Http\Io\Clock')->disableOriginalConstructor()->getMock();
+
+        $parser = new RequestHeaderParser($clock);
         $parser->on('headers', $this->expectCallableNever());
         $parser->on('error', function ($message) use (&$error) {
             $error = $message;
@@ -445,7 +485,9 @@ public function testInvalidAbsoluteFormWithFragmentEmitsError()
     {
         $error = null;
 
-        $parser = new RequestHeaderParser();
+        $clock = $this->getMockBuilder('React\Http\Io\Clock')->disableOriginalConstructor()->getMock();
+
+        $parser = new RequestHeaderParser($clock);
         $parser->on('headers', $this->expectCallableNever());
         $parser->on('error', function ($message) use (&$error) {
             $error = $message;
@@ -464,7 +506,9 @@ public function testInvalidHeaderContainsFullUri()
     {
         $error = null;
 
-        $parser = new RequestHeaderParser();
+        $clock = $this->getMockBuilder('React\Http\Io\Clock')->disableOriginalConstructor()->getMock();
+
+        $parser = new RequestHeaderParser($clock);
         $parser->on('headers', $this->expectCallableNever());
         $parser->on('error', function ($message) use (&$error) {
             $error = $message;
@@ -483,7 +527,9 @@ public function testInvalidAbsoluteFormWithHostHeaderEmpty()
     {
         $error = null;
 
-        $parser = new RequestHeaderParser();
+        $clock = $this->getMockBuilder('React\Http\Io\Clock')->disableOriginalConstructor()->getMock();
+
+        $parser = new RequestHeaderParser($clock);
         $parser->on('headers', $this->expectCallableNever());
         $parser->on('error', function ($message) use (&$error) {
             $error = $message;
@@ -502,7 +548,9 @@ public function testInvalidConnectRequestWithNonAuthorityForm()
     {
         $error = null;
 
-        $parser = new RequestHeaderParser();
+        $clock = $this->getMockBuilder('React\Http\Io\Clock')->disableOriginalConstructor()->getMock();
+
+        $parser = new RequestHeaderParser($clock);
         $parser->on('headers', $this->expectCallableNever());
         $parser->on('error', function ($message) use (&$error) {
             $error = $message;
@@ -521,7 +569,9 @@ public function testInvalidHttpVersion()
     {
         $error = null;
 
-        $parser = new RequestHeaderParser();
+        $clock = $this->getMockBuilder('React\Http\Io\Clock')->disableOriginalConstructor()->getMock();
+
+        $parser = new RequestHeaderParser($clock);
         $parser->on('headers', $this->expectCallableNever());
         $parser->on('error', function ($message) use (&$error) {
             $error = $message;
@@ -541,7 +591,9 @@ public function testInvalidContentLengthRequestHeaderWillEmitError()
     {
         $error = null;
 
-        $parser = new RequestHeaderParser();
+        $clock = $this->getMockBuilder('React\Http\Io\Clock')->disableOriginalConstructor()->getMock();
+
+        $parser = new RequestHeaderParser($clock);
         $parser->on('headers', $this->expectCallableNever());
         $parser->on('error', function ($message) use (&$error) {
             $error = $message;
@@ -561,7 +613,9 @@ public function testInvalidRequestWithMultipleContentLengthRequestHeadersWillEmi
     {
         $error = null;
 
-        $parser = new RequestHeaderParser();
+        $clock = $this->getMockBuilder('React\Http\Io\Clock')->disableOriginalConstructor()->getMock();
+
+        $parser = new RequestHeaderParser($clock);
         $parser->on('headers', $this->expectCallableNever());
         $parser->on('error', function ($message) use (&$error) {
             $error = $message;
@@ -581,7 +635,9 @@ public function testInvalidTransferEncodingRequestHeaderWillEmitError()
     {
         $error = null;
 
-        $parser = new RequestHeaderParser();
+        $clock = $this->getMockBuilder('React\Http\Io\Clock')->disableOriginalConstructor()->getMock();
+
+        $parser = new RequestHeaderParser($clock);
         $parser->on('headers', $this->expectCallableNever());
         $parser->on('error', function ($message) use (&$error) {
             $error = $message;
@@ -601,7 +657,9 @@ public function testInvalidRequestWithBothTransferEncodingAndContentLengthWillEm
     {
         $error = null;
 
-        $parser = new RequestHeaderParser();
+        $clock = $this->getMockBuilder('React\Http\Io\Clock')->disableOriginalConstructor()->getMock();
+
+        $parser = new RequestHeaderParser($clock);
         $parser->on('headers', $this->expectCallableNever());
         $parser->on('error', function ($message) use (&$error) {
             $error = $message;
@@ -621,7 +679,10 @@ public function testServerParamsWillBeSetOnHttpsRequest()
     {
         $request = null;
 
-        $parser = new RequestHeaderParser();
+        $clock = $this->getMockBuilder('React\Http\Io\Clock')->disableOriginalConstructor()->getMock();
+        $clock->expects($this->once())->method('now')->willReturn(1652972091.3958);
+
+        $parser = new RequestHeaderParser($clock);
 
         $parser->on('headers', function ($parsedRequest) use (&$request) {
             $request = $parsedRequest;
@@ -637,8 +698,8 @@ public function testServerParamsWillBeSetOnHttpsRequest()
         $serverParams = $request->getServerParams();
 
         $this->assertEquals('on', $serverParams['HTTPS']);
-        $this->assertNotEmpty($serverParams['REQUEST_TIME']);
-        $this->assertNotEmpty($serverParams['REQUEST_TIME_FLOAT']);
+        $this->assertEquals(1652972091, $serverParams['REQUEST_TIME']);
+        $this->assertEquals(1652972091.3958, $serverParams['REQUEST_TIME_FLOAT']);
 
         $this->assertEquals('127.1.1.1', $serverParams['SERVER_ADDR']);
         $this->assertEquals('8000', $serverParams['SERVER_PORT']);
@@ -651,7 +712,10 @@ public function testServerParamsWillBeSetOnHttpRequest()
     {
         $request = null;
 
-        $parser = new RequestHeaderParser();
+        $clock = $this->getMockBuilder('React\Http\Io\Clock')->disableOriginalConstructor()->getMock();
+        $clock->expects($this->once())->method('now')->willReturn(1652972091.3958);
+
+        $parser = new RequestHeaderParser($clock);
 
         $parser->on('headers', function ($parsedRequest) use (&$request) {
             $request = $parsedRequest;
@@ -667,8 +731,8 @@ public function testServerParamsWillBeSetOnHttpRequest()
         $serverParams = $request->getServerParams();
 
         $this->assertArrayNotHasKey('HTTPS', $serverParams);
-        $this->assertNotEmpty($serverParams['REQUEST_TIME']);
-        $this->assertNotEmpty($serverParams['REQUEST_TIME_FLOAT']);
+        $this->assertEquals(1652972091, $serverParams['REQUEST_TIME']);
+        $this->assertEquals(1652972091.3958, $serverParams['REQUEST_TIME_FLOAT']);
 
         $this->assertEquals('127.1.1.1', $serverParams['SERVER_ADDR']);
         $this->assertEquals('8000', $serverParams['SERVER_PORT']);
@@ -681,7 +745,10 @@ public function testServerParamsWillNotSetRemoteAddressForUnixDomainSockets()
     {
         $request = null;
 
-        $parser = new RequestHeaderParser();
+        $clock = $this->getMockBuilder('React\Http\Io\Clock')->disableOriginalConstructor()->getMock();
+        $clock->expects($this->once())->method('now')->willReturn(1652972091.3958);
+
+        $parser = new RequestHeaderParser($clock);
 
         $parser->on('headers', function ($parsedRequest) use (&$request) {
             $request = $parsedRequest;
@@ -697,8 +764,8 @@ public function testServerParamsWillNotSetRemoteAddressForUnixDomainSockets()
         $serverParams = $request->getServerParams();
 
         $this->assertArrayNotHasKey('HTTPS', $serverParams);
-        $this->assertNotEmpty($serverParams['REQUEST_TIME']);
-        $this->assertNotEmpty($serverParams['REQUEST_TIME_FLOAT']);
+        $this->assertEquals(1652972091, $serverParams['REQUEST_TIME']);
+        $this->assertEquals(1652972091.3958, $serverParams['REQUEST_TIME_FLOAT']);
 
         $this->assertArrayNotHasKey('SERVER_ADDR', $serverParams);
         $this->assertArrayNotHasKey('SERVER_PORT', $serverParams);
@@ -715,7 +782,10 @@ public function testServerParamsWontBeSetOnMissingUrls()
 
         $request = null;
 
-        $parser = new RequestHeaderParser();
+        $clock = $this->getMockBuilder('React\Http\Io\Clock')->disableOriginalConstructor()->getMock();
+        $clock->expects($this->once())->method('now')->willReturn(1652972091.3958);
+
+        $parser = new RequestHeaderParser($clock);
 
         $parser->on('headers', function ($parsedRequest) use (&$request) {
             $request = $parsedRequest;
@@ -728,8 +798,8 @@ public function testServerParamsWontBeSetOnMissingUrls()
 
         $serverParams = $request->getServerParams();
 
-        $this->assertNotEmpty($serverParams['REQUEST_TIME']);
-        $this->assertNotEmpty($serverParams['REQUEST_TIME_FLOAT']);
+        $this->assertEquals(1652972091, $serverParams['REQUEST_TIME']);
+        $this->assertEquals(1652972091.3958, $serverParams['REQUEST_TIME_FLOAT']);
 
         $this->assertArrayNotHasKey('SERVER_ADDR', $serverParams);
         $this->assertArrayNotHasKey('SERVER_PORT', $serverParams);
@@ -742,7 +812,9 @@ public function testQueryParmetersWillBeSet()
     {
         $request = null;
 
-        $parser = new RequestHeaderParser();
+        $clock = $this->getMockBuilder('React\Http\Io\Clock')->disableOriginalConstructor()->getMock();
+
+        $parser = new RequestHeaderParser($clock);
 
         $parser->on('headers', function ($parsedRequest) use (&$request) {
             $request = $parsedRequest;
diff --git a/tests/Io/StreamingServerTest.php b/tests/Io/StreamingServerTest.php
index 45729f2b..2703362a 100644
--- a/tests/Io/StreamingServerTest.php
+++ b/tests/Io/StreamingServerTest.php
@@ -2292,12 +2292,20 @@ function ($data) use (&$buffer) {
         $this->assertContainsString("5\r\nhello\r\n", $buffer);
     }
 
-    public function testResponseWithoutExplicitDateHeaderWillAddCurrentDate()
+    public function testResponseWithoutExplicitDateHeaderWillAddCurrentDateFromClock()
     {
         $server = new StreamingServer(Loop::get(), function (ServerRequestInterface $request) {
             return new Response();
         });
 
+        $ref = new \ReflectionProperty($server, 'clock');
+        $ref->setAccessible(true);
+        $clock = $ref->getValue($server);
+
+        $ref = new \ReflectionProperty($clock, 'now');
+        $ref->setAccessible(true);
+        $ref->setValue($clock, 1652972091.3958);
+
         $buffer = '';
             $this->connection
             ->expects($this->any())
@@ -2318,11 +2326,11 @@ function ($data) use (&$buffer) {
         $this->connection->emit('data', array($data));
 
         $this->assertContainsString("HTTP/1.1 200 OK\r\n", $buffer);
-        $this->assertContainsString("Date:", $buffer);
+        $this->assertContainsString("Date: Thu, 19 May 2022 14:54:51 GMT\r\n", $buffer);
         $this->assertContainsString("\r\n\r\n", $buffer);
     }
 
-    public function testResponseWIthCustomDateHeaderOverwritesDefault()
+    public function testResponseWithCustomDateHeaderOverwritesDefault()
     {
         $server = new StreamingServer(Loop::get(), function (ServerRequestInterface $request) {
             return new Response(
@@ -3022,7 +3030,8 @@ public function testRequestCookieWithSeparatorWillBeAddedToServerRequest()
         $this->assertEquals(array('hello' => 'world', 'test' => 'abc'), $requestValidation->getCookieParams());
     }
 
-    public function testRequestCookieWithCommaValueWillBeAddedToServerRequest() {
+    public function testRequestCookieWithCommaValueWillBeAddedToServerRequest()
+    {
         $requestValidation = null;
         $server = new StreamingServer(Loop::get(), function (ServerRequestInterface $request) use (&$requestValidation) {
             $requestValidation = $request;
@@ -3045,7 +3054,7 @@ public function testNewConnectionWillInvokeParserOnce()
     {
         $server = new StreamingServer(Loop::get(), $this->expectCallableNever());
 
-        $parser = $this->getMockBuilder('React\Http\Io\RequestHeaderParser')->getMock();
+        $parser = $this->getMockBuilder('React\Http\Io\RequestHeaderParser')->disableOriginalConstructor()->getMock();
         $parser->expects($this->once())->method('handle');
 
         $ref = new \ReflectionProperty($server, 'parser');
@@ -3062,7 +3071,7 @@ public function testNewConnectionWillInvokeParserOnceAndInvokeRequestHandlerWhen
 
         $server = new StreamingServer(Loop::get(), $this->expectCallableOnceWith($request));
 
-        $parser = $this->getMockBuilder('React\Http\Io\RequestHeaderParser')->getMock();
+        $parser = $this->getMockBuilder('React\Http\Io\RequestHeaderParser')->disableOriginalConstructor()->getMock();
         $parser->expects($this->once())->method('handle');
 
         $ref = new \ReflectionProperty($server, 'parser');
@@ -3085,7 +3094,7 @@ public function testNewConnectionWillInvokeParserOnceAndInvokeRequestHandlerWhen
 
         $server = new StreamingServer(Loop::get(), $this->expectCallableOnceWith($request));
 
-        $parser = $this->getMockBuilder('React\Http\Io\RequestHeaderParser')->getMock();
+        $parser = $this->getMockBuilder('React\Http\Io\RequestHeaderParser')->disableOriginalConstructor()->getMock();
         $parser->expects($this->once())->method('handle');
 
         $ref = new \ReflectionProperty($server, 'parser');
@@ -3110,7 +3119,7 @@ public function testNewConnectionWillInvokeParserOnceAndInvokeRequestHandlerWhen
             return new Response(200, array('Connection' => 'close'));
         });
 
-        $parser = $this->getMockBuilder('React\Http\Io\RequestHeaderParser')->getMock();
+        $parser = $this->getMockBuilder('React\Http\Io\RequestHeaderParser')->disableOriginalConstructor()->getMock();
         $parser->expects($this->once())->method('handle');
 
         $ref = new \ReflectionProperty($server, 'parser');
@@ -3135,7 +3144,7 @@ public function testNewConnectionWillInvokeParserTwiceAfterInvokingRequestHandle
             return new Response();
         });
 
-        $parser = $this->getMockBuilder('React\Http\Io\RequestHeaderParser')->getMock();
+        $parser = $this->getMockBuilder('React\Http\Io\RequestHeaderParser')->disableOriginalConstructor()->getMock();
         $parser->expects($this->exactly(2))->method('handle');
 
         $ref = new \ReflectionProperty($server, 'parser');
@@ -3160,7 +3169,7 @@ public function testNewConnectionWillInvokeParserTwiceAfterInvokingRequestHandle
             return new Response();
         });
 
-        $parser = $this->getMockBuilder('React\Http\Io\RequestHeaderParser')->getMock();
+        $parser = $this->getMockBuilder('React\Http\Io\RequestHeaderParser')->disableOriginalConstructor()->getMock();
         $parser->expects($this->exactly(2))->method('handle');
 
         $ref = new \ReflectionProperty($server, 'parser');
@@ -3186,7 +3195,7 @@ public function testNewConnectionWillInvokeParserOnceAfterInvokingRequestHandler
             return new Response(200, array(), $body);
         });
 
-        $parser = $this->getMockBuilder('React\Http\Io\RequestHeaderParser')->getMock();
+        $parser = $this->getMockBuilder('React\Http\Io\RequestHeaderParser')->disableOriginalConstructor()->getMock();
         $parser->expects($this->once())->method('handle');
 
         $ref = new \ReflectionProperty($server, 'parser');
@@ -3212,7 +3221,7 @@ public function testNewConnectionWillInvokeParserTwiceAfterInvokingRequestHandle
             return new Response(200, array(), $body);
         });
 
-        $parser = $this->getMockBuilder('React\Http\Io\RequestHeaderParser')->getMock();
+        $parser = $this->getMockBuilder('React\Http\Io\RequestHeaderParser')->disableOriginalConstructor()->getMock();
         $parser->expects($this->exactly(2))->method('handle');
 
         $ref = new \ReflectionProperty($server, 'parser');