diff --git a/src/Kestrel.Core/Internal/Http/DateHeaderValueManager.cs b/src/Kestrel.Core/Internal/Http/DateHeaderValueManager.cs
index b2cb874364..ee82fd1bc1 100644
--- a/src/Kestrel.Core/Internal/Http/DateHeaderValueManager.cs
+++ b/src/Kestrel.Core/Internal/Http/DateHeaderValueManager.cs
@@ -22,14 +22,14 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
         /// Initializes a new instance of the <see cref="DateHeaderValueManager"/> class.
         /// </summary>
         public DateHeaderValueManager()
-            : this(systemClock: new SystemClock())
+            : this(DateTimeOffset.UtcNow)
         {
         }
 
         // Internal for testing
-        internal DateHeaderValueManager(ISystemClock systemClock)
+        internal DateHeaderValueManager(DateTimeOffset initialUtcNow)
         {
-            SetDateValues(systemClock.UtcNow);
+            SetDateValues(initialUtcNow);
         }
 
         /// <summary>
diff --git a/src/Kestrel.Core/Internal/Infrastructure/Heartbeat.cs b/src/Kestrel.Core/Internal/Infrastructure/Heartbeat.cs
index fb0f17d83b..5937002304 100644
--- a/src/Kestrel.Core/Internal/Infrastructure/Heartbeat.cs
+++ b/src/Kestrel.Core/Internal/Infrastructure/Heartbeat.cs
@@ -19,18 +19,13 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Infrastructure
         private Timer _timer;
         private int _executingOnHeartbeat;
 
-        public Heartbeat(IHeartbeatHandler[] callbacks, ISystemClock systemClock, IDebugger debugger, IKestrelTrace trace): this(callbacks, systemClock, debugger, trace, Interval)
-        {
-
-        }
-
-        internal Heartbeat(IHeartbeatHandler[] callbacks, ISystemClock systemClock, IDebugger debugger, IKestrelTrace trace, TimeSpan interval)
+        public Heartbeat(IHeartbeatHandler[] callbacks, ISystemClock systemClock, IDebugger debugger, IKestrelTrace trace)
         {
             _callbacks = callbacks;
             _systemClock = systemClock;
             _debugger = debugger;
             _trace = trace;
-            _interval = interval;
+            _interval = Interval;
         }
 
         public void Start()
diff --git a/src/Kestrel.Core/Internal/Infrastructure/HeartbeatManager.cs b/src/Kestrel.Core/Internal/Infrastructure/HeartbeatManager.cs
index bc54e73385..98d3585921 100644
--- a/src/Kestrel.Core/Internal/Infrastructure/HeartbeatManager.cs
+++ b/src/Kestrel.Core/Internal/Infrastructure/HeartbeatManager.cs
@@ -11,9 +11,10 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Infrastructure
         private readonly Action<KestrelConnection> _walkCallback;
         private DateTimeOffset _now;
 
-        public HeartbeatManager(ConnectionManager connectionManager)
+        public HeartbeatManager(ConnectionManager connectionManager, DateTimeOffset initialUtcNow)
         {
             _connectionManager = connectionManager;
+            _now = initialUtcNow;
             _walkCallback = WalkCallback;
         }
 
diff --git a/src/Kestrel.Core/KestrelServer.cs b/src/Kestrel.Core/KestrelServer.cs
index cc21f738d0..e90188a6eb 100644
--- a/src/Kestrel.Core/KestrelServer.cs
+++ b/src/Kestrel.Core/KestrelServer.cs
@@ -71,8 +71,9 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core
                 trace,
                 serverOptions.Limits.MaxConcurrentUpgradedConnections);
 
-            var heartbeatManager = new HeartbeatManager(connectionManager);
-            var dateHeaderValueManager = new DateHeaderValueManager(heartbeatManager);
+            var now = DateTimeOffset.UtcNow;
+            var heartbeatManager = new HeartbeatManager(connectionManager, now);
+            var dateHeaderValueManager = new DateHeaderValueManager(now);
             var heartbeat = new Heartbeat(
                 new IHeartbeatHandler[] { dateHeaderValueManager, heartbeatManager },
                 new SystemClock(),
diff --git a/test/Kestrel.Core.Tests/DateHeaderValueManagerTests.cs b/test/Kestrel.Core.Tests/DateHeaderValueManagerTests.cs
index 3d1e880765..adf2971c2c 100644
--- a/test/Kestrel.Core.Tests/DateHeaderValueManagerTests.cs
+++ b/test/Kestrel.Core.Tests/DateHeaderValueManagerTests.cs
@@ -24,12 +24,8 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Tests
         public void GetDateHeaderValue_ReturnsDateValueInRFC1123Format()
         {
             var now = DateTimeOffset.UtcNow;
-            var systemClock = new MockSystemClock
-            {
-                UtcNow = now
-            };
 
-            var dateHeaderValueManager = new DateHeaderValueManager(systemClock);
+            var dateHeaderValueManager = new DateHeaderValueManager(now);
             Assert.Equal(now.ToString(Rfc1123DateFormat), dateHeaderValueManager.GetDateHeaderValues().String);
         }
 
@@ -43,7 +39,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Tests
                 UtcNow = now
             };
 
-            var dateHeaderValueManager = new DateHeaderValueManager(systemClock);
+            var dateHeaderValueManager = new DateHeaderValueManager(now);
             var testKestrelTrace = new TestKestrelTrace();
 
             using (var heartbeat = new Heartbeat(new IHeartbeatHandler[] { dateHeaderValueManager }, systemClock, DebuggerWrapper.Singleton, testKestrelTrace))
@@ -53,7 +49,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Tests
                 Assert.Equal(now.ToString(Rfc1123DateFormat), dateHeaderValueManager.GetDateHeaderValues().String);
             }
 
-            Assert.Equal(1, systemClock.UtcNowCalled);
+            Assert.Equal(0, systemClock.UtcNowCalled);
         }
 
         [Fact]
@@ -66,7 +62,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Tests
                 UtcNow = now
             };
 
-            var dateHeaderValueManager = new DateHeaderValueManager(systemClock);
+            var dateHeaderValueManager = new DateHeaderValueManager(now);
             var testKestrelTrace = new TestKestrelTrace();
 
             var mockHeartbeatHandler = new Mock<IHeartbeatHandler>();
@@ -83,7 +79,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Tests
                 heartbeat.OnHeartbeat();
 
                 Assert.Equal(future.ToString(Rfc1123DateFormat), dateHeaderValueManager.GetDateHeaderValues().String);
-                Assert.True(systemClock.UtcNowCalled >= 2);
+                Assert.Equal(2, systemClock.UtcNowCalled);
             }
         }
 
@@ -97,7 +93,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Tests
                 UtcNow = now
             };
 
-            var dateHeaderValueManager = new DateHeaderValueManager(systemClock);
+            var dateHeaderValueManager = new DateHeaderValueManager(now);
             var testKestrelTrace = new TestKestrelTrace();
 
             using (var heatbeat = new Heartbeat(new IHeartbeatHandler[] { dateHeaderValueManager }, systemClock, DebuggerWrapper.Singleton, testKestrelTrace))
diff --git a/test/Kestrel.InMemory.FunctionalTests/HttpsTests.cs b/test/Kestrel.InMemory.FunctionalTests/HttpsTests.cs
index 9e52de9f12..1f3039abbb 100644
--- a/test/Kestrel.InMemory.FunctionalTests/HttpsTests.cs
+++ b/test/Kestrel.InMemory.FunctionalTests/HttpsTests.cs
@@ -312,7 +312,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.InMemory.FunctionalTests
             LoggerFactory.AddProvider(loggerProvider);
 
             var testContext = new TestServiceContext(LoggerFactory);
-            var heartbeatManager = new HeartbeatManager(testContext.ConnectionManager);
+            var heartbeatManager = new HeartbeatManager(testContext.ConnectionManager, testContext.SystemClock.UtcNow);
 
             var handshakeStartedTcs = new TaskCompletionSource<object>(TaskCreationOptions.RunContinuationsAsynchronously);
             TimeSpan handshakeTimeout = default;
diff --git a/test/Kestrel.InMemory.FunctionalTests/KeepAliveTimeoutTests.cs b/test/Kestrel.InMemory.FunctionalTests/KeepAliveTimeoutTests.cs
index 716ff9583a..f462b0716c 100644
--- a/test/Kestrel.InMemory.FunctionalTests/KeepAliveTimeoutTests.cs
+++ b/test/Kestrel.InMemory.FunctionalTests/KeepAliveTimeoutTests.cs
@@ -27,7 +27,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.InMemory.FunctionalTests
         public async Task ConnectionClosedWhenKeepAliveTimeoutExpires()
         {
             var testContext = new TestServiceContext(LoggerFactory);
-            var heartbeatManager = new HeartbeatManager(testContext.ConnectionManager);
+            var heartbeatManager = new HeartbeatManager(testContext.ConnectionManager, testContext.SystemClock.UtcNow);
 
             using (var server = CreateServer(testContext))
             using (var connection = server.CreateConnection())
@@ -51,7 +51,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.InMemory.FunctionalTests
         public async Task ConnectionKeptAliveBetweenRequests()
         {
             var testContext = new TestServiceContext(LoggerFactory);
-            var heartbeatManager = new HeartbeatManager(testContext.ConnectionManager);
+            var heartbeatManager = new HeartbeatManager(testContext.ConnectionManager, testContext.SystemClock.UtcNow);
 
             using (var server = CreateServer(testContext))
             using (var connection = server.CreateConnection())
@@ -76,7 +76,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.InMemory.FunctionalTests
         public async Task ConnectionNotTimedOutWhileRequestBeingSent()
         {
             var testContext = new TestServiceContext(LoggerFactory);
-            var heartbeatManager = new HeartbeatManager(testContext.ConnectionManager);
+            var heartbeatManager = new HeartbeatManager(testContext.ConnectionManager, testContext.SystemClock.UtcNow);
 
             using (var server = CreateServer(testContext))
             using (var connection = server.CreateConnection())
@@ -113,7 +113,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.InMemory.FunctionalTests
         private async Task ConnectionNotTimedOutWhileAppIsRunning()
         {
             var testContext = new TestServiceContext(LoggerFactory);
-            var heartbeatManager = new HeartbeatManager(testContext.ConnectionManager);
+            var heartbeatManager = new HeartbeatManager(testContext.ConnectionManager, testContext.SystemClock.UtcNow);
             var cts = new CancellationTokenSource();
 
             using (var server = CreateServer(testContext, longRunningCt: cts.Token))
@@ -150,7 +150,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.InMemory.FunctionalTests
         private async Task ConnectionTimesOutWhenOpenedButNoRequestSent()
         {
             var testContext = new TestServiceContext(LoggerFactory);
-            var heartbeatManager = new HeartbeatManager(testContext.ConnectionManager);
+            var heartbeatManager = new HeartbeatManager(testContext.ConnectionManager, testContext.SystemClock.UtcNow);
 
             using (var server = CreateServer(testContext))
             using (var connection = server.CreateConnection())
@@ -167,7 +167,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.InMemory.FunctionalTests
         private async Task KeepAliveTimeoutDoesNotApplyToUpgradedConnections()
         {
             var testContext = new TestServiceContext(LoggerFactory);
-            var heartbeatManager = new HeartbeatManager(testContext.ConnectionManager);
+            var heartbeatManager = new HeartbeatManager(testContext.ConnectionManager, testContext.SystemClock.UtcNow);
             var cts = new CancellationTokenSource();
 
             using (var server = CreateServer(testContext, upgradeCt: cts.Token))
diff --git a/test/Kestrel.InMemory.FunctionalTests/RequestBodyTimeoutTests.cs b/test/Kestrel.InMemory.FunctionalTests/RequestBodyTimeoutTests.cs
index f8946d707e..b0fe3d9017 100644
--- a/test/Kestrel.InMemory.FunctionalTests/RequestBodyTimeoutTests.cs
+++ b/test/Kestrel.InMemory.FunctionalTests/RequestBodyTimeoutTests.cs
@@ -22,7 +22,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.InMemory.FunctionalTests
         {
             var gracePeriod = TimeSpan.FromSeconds(5);
             var serviceContext = new TestServiceContext(LoggerFactory);
-            var heartbeatManager = new HeartbeatManager(serviceContext.ConnectionManager);
+            var heartbeatManager = new HeartbeatManager(serviceContext.ConnectionManager, serviceContext.SystemClock.UtcNow);
 
             var appRunningEvent = new TaskCompletionSource<object>(TaskCreationOptions.RunContinuationsAsynchronously);
 
@@ -136,7 +136,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.InMemory.FunctionalTests
         {
             var gracePeriod = TimeSpan.FromSeconds(5);
             var serviceContext = new TestServiceContext(LoggerFactory);
-            var heartbeatManager = new HeartbeatManager(serviceContext.ConnectionManager);
+            var heartbeatManager = new HeartbeatManager(serviceContext.ConnectionManager, serviceContext.SystemClock.UtcNow);
 
             var appRunningTcs = new TaskCompletionSource<object>(TaskCreationOptions.RunContinuationsAsynchronously);
             var exceptionSwallowedTcs = new TaskCompletionSource<object>(TaskCreationOptions.RunContinuationsAsynchronously);
diff --git a/test/Kestrel.InMemory.FunctionalTests/RequestHeadersTimeoutTests.cs b/test/Kestrel.InMemory.FunctionalTests/RequestHeadersTimeoutTests.cs
index e5fd714179..5bd803a6dc 100644
--- a/test/Kestrel.InMemory.FunctionalTests/RequestHeadersTimeoutTests.cs
+++ b/test/Kestrel.InMemory.FunctionalTests/RequestHeadersTimeoutTests.cs
@@ -26,7 +26,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.InMemory.FunctionalTests
         public async Task ConnectionAbortedWhenRequestHeadersNotReceivedInTime(string headers)
         {
             var testContext = new TestServiceContext(LoggerFactory);
-            var heartbeatManager = new HeartbeatManager(testContext.ConnectionManager);
+            var heartbeatManager = new HeartbeatManager(testContext.ConnectionManager, testContext.SystemClock.UtcNow);
 
             using (var server = CreateServer(testContext))
             using (var connection = server.CreateConnection())
@@ -47,7 +47,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.InMemory.FunctionalTests
         public async Task RequestHeadersTimeoutCanceledAfterHeadersReceived()
         {
             var testContext = new TestServiceContext(LoggerFactory);
-            var heartbeatManager = new HeartbeatManager(testContext.ConnectionManager);
+            var heartbeatManager = new HeartbeatManager(testContext.ConnectionManager, testContext.SystemClock.UtcNow);
 
             using (var server = CreateServer(testContext))
             using (var connection = server.CreateConnection())
@@ -76,7 +76,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.InMemory.FunctionalTests
         public async Task ConnectionAbortedWhenRequestLineNotReceivedInTime(string requestLine)
         {
             var testContext = new TestServiceContext(LoggerFactory);
-            var heartbeatManager = new HeartbeatManager(testContext.ConnectionManager);
+            var heartbeatManager = new HeartbeatManager(testContext.ConnectionManager, testContext.SystemClock.UtcNow);
 
             using (var server = CreateServer(testContext))
             using (var connection = server.CreateConnection())
@@ -95,7 +95,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.InMemory.FunctionalTests
         public async Task TimeoutNotResetOnEachRequestLineCharacterReceived()
         {
             var testContext = new TestServiceContext(LoggerFactory);
-            var heartbeatManager = new HeartbeatManager(testContext.ConnectionManager);
+            var heartbeatManager = new HeartbeatManager(testContext.ConnectionManager, testContext.SystemClock.UtcNow);
 
             using (var server = CreateServer(testContext))
             using (var connection = server.CreateConnection())
diff --git a/test/Kestrel.InMemory.FunctionalTests/RequestTests.cs b/test/Kestrel.InMemory.FunctionalTests/RequestTests.cs
index 34f6b92333..0edb95b273 100644
--- a/test/Kestrel.InMemory.FunctionalTests/RequestTests.cs
+++ b/test/Kestrel.InMemory.FunctionalTests/RequestTests.cs
@@ -877,7 +877,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.InMemory.FunctionalTests
             var appEvent = new TaskCompletionSource<object>(TaskCreationOptions.RunContinuationsAsynchronously);
             var delayEvent = new TaskCompletionSource<object>(TaskCreationOptions.RunContinuationsAsynchronously);
             var serviceContext = new TestServiceContext(LoggerFactory);
-            var heartbeatManager = new HeartbeatManager(serviceContext.ConnectionManager);
+            var heartbeatManager = new HeartbeatManager(serviceContext.ConnectionManager, serviceContext.SystemClock.UtcNow);
 
             using (var server = new TestServer(async context =>
             {
diff --git a/test/Kestrel.Transport.FunctionalTests/RequestTests.cs b/test/Kestrel.Transport.FunctionalTests/RequestTests.cs
index fc5a5d382b..e194331df1 100644
--- a/test/Kestrel.Transport.FunctionalTests/RequestTests.cs
+++ b/test/Kestrel.Transport.FunctionalTests/RequestTests.cs
@@ -100,7 +100,9 @@ namespace Microsoft.AspNetCore.Server.Kestrel.FunctionalTests
                 using (var socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp))
                 {
                     socket.Connect(new IPEndPoint(IPAddress.Loopback, host.GetPort()));
-                    socket.Send(Encoding.ASCII.GetBytes($"POST / HTTP/1.0\r\nContent-Length: {contentLength}\r\n\r\n"));
+                    socket.Send(Encoding.ASCII.GetBytes("POST / HTTP/1.0\r\n"));
+                    Thread.Sleep(5000);
+                    socket.Send(Encoding.ASCII.GetBytes($"Content-Length: {contentLength}\r\n\r\n"));
 
                     var contentBytes = new byte[bufferLength];
 
diff --git a/test/shared/TestServiceContext.cs b/test/shared/TestServiceContext.cs
index 356164e725..3e833a9e5e 100644
--- a/test/shared/TestServiceContext.cs
+++ b/test/shared/TestServiceContext.cs
@@ -41,16 +41,17 @@ namespace Microsoft.AspNetCore.Testing
 
         public void InitializeHeartbeat()
         {
-            MockSystemClock = null;
-            SystemClock = new SystemClock();
-            DateHeaderValueManager = new DateHeaderValueManager(SystemClock);
-
-            var heartbeatManager = new HeartbeatManager(ConnectionManager);
+            var now = DateTimeOffset.UtcNow;
+            var heartbeatManager = new HeartbeatManager(ConnectionManager, now);
+            DateHeaderValueManager = new DateHeaderValueManager(now);
             Heartbeat = new Heartbeat(
                 new IHeartbeatHandler[] { DateHeaderValueManager, heartbeatManager },
-                SystemClock,
+                new SystemClock(),
                 DebuggerWrapper.Singleton,
                 Log);
+
+            MockSystemClock = null;
+            SystemClock = heartbeatManager;
         }
 
         private void Initialize(ILoggerFactory loggerFactory, IKestrelTrace kestrelTrace)
@@ -60,7 +61,7 @@ namespace Microsoft.AspNetCore.Testing
             Scheduler = PipeScheduler.ThreadPool;
             MockSystemClock = new MockSystemClock();
             SystemClock = MockSystemClock;
-            DateHeaderValueManager = new DateHeaderValueManager(MockSystemClock);
+            DateHeaderValueManager = new DateHeaderValueManager(MockSystemClock.UtcNow);
             ConnectionManager = new ConnectionManager(Log, ResourceCounter.Unlimited);
             HttpParser = new HttpParser<Http1ParsingHandler>(Log.IsEnabled(LogLevel.Information));
             ServerOptions = new KestrelServerOptions