diff --git a/.gas-snapshot b/.gas-snapshot
index 5b631607..b1e837ea 100644
--- a/.gas-snapshot
+++ b/.gas-snapshot
@@ -8,13 +8,13 @@ IBCTest:testBenchmarkRecvPacket() (gas: 158870)
 IBCTest:testBenchmarkSendPacket() (gas: 128432)
 IBCTest:testBenchmarkUpdateMockClient() (gas: 160229)
 IBCTest:testToUint128((uint64,uint64)) (runs: 256, μ: 947, ~: 947)
-TestICS02:testCreateClient() (gas: 36496843)
-TestICS02:testInvalidCreateClient() (gas: 36394062)
-TestICS02:testInvalidUpdateClient() (gas: 36392970)
-TestICS02:testRegisterClient() (gas: 36048636)
-TestICS02:testRegisterClientDuplicatedClientType() (gas: 36033945)
-TestICS02:testRegisterClientInvalidClientType() (gas: 36063406)
-TestICS02:testUpdateClient() (gas: 36561170)
+TestICS02:testCreateClient() (gas: 36540928)
+TestICS02:testInvalidCreateClient() (gas: 36438147)
+TestICS02:testInvalidUpdateClient() (gas: 36437055)
+TestICS02:testRegisterClient() (gas: 36092721)
+TestICS02:testRegisterClientDuplicatedClientType() (gas: 36078030)
+TestICS02:testRegisterClientInvalidClientType() (gas: 36107491)
+TestICS02:testUpdateClient() (gas: 36605255)
 TestICS03Handshake:testConnOpenAck() (gas: 1858230)
 TestICS03Handshake:testConnOpenConfirm() (gas: 2054143)
 TestICS03Handshake:testConnOpenInit() (gas: 1429838)
@@ -41,9 +41,9 @@ TestICS04Handshake:testInvalidChanOpenInit() (gas: 1760558)
 TestICS04Handshake:testInvalidChanOpenTry() (gas: 1775528)
 TestICS04Packet:testAcknowledgementPacket() (gas: 3351116)
 TestICS04Packet:testInvalidSendPacket() (gas: 3551583)
-TestICS04Packet:testRecvPacket() (gas: 10996130)
+TestICS04Packet:testRecvPacket() (gas: 10996942)
 TestICS04Packet:testRecvPacketTimeoutHeight() (gas: 3259727)
-TestICS04Packet:testRecvPacketTimeoutTimestamp() (gas: 3278877)
+TestICS04Packet:testRecvPacketTimeoutTimestamp() (gas: 3279103)
 TestICS04Packet:testSendPacket() (gas: 6412442)
 TestICS04Packet:testTimeoutOnClose() (gas: 3553289)
 TestICS04Upgrade:testUpgradeAuthorityCancel() (gas: 46742335)
@@ -58,9 +58,9 @@ TestICS04Upgrade:testUpgradeOutOfSync() (gas: 3903220)
 TestICS04Upgrade:testUpgradeRelaySuccessAtCounterpartyFlushComplete() (gas: 5237770)
 TestICS04Upgrade:testUpgradeRelaySuccessAtFlushing() (gas: 5610957)
 TestICS04Upgrade:testUpgradeSendPacketFailAtFlushingOrFlushComplete() (gas: 4071025)
-TestICS04Upgrade:testUpgradeTimeoutAbortAck() (gas: 17681581)
-TestICS04Upgrade:testUpgradeTimeoutAbortConfirm() (gas: 21317741)
-TestICS04Upgrade:testUpgradeTimeoutUpgrade() (gas: 44264077)
+TestICS04Upgrade:testUpgradeTimeoutAbortAck() (gas: 17694261)
+TestICS04Upgrade:testUpgradeTimeoutAbortConfirm() (gas: 21333518)
+TestICS04Upgrade:testUpgradeTimeoutUpgrade() (gas: 71049040)
 TestICS04Upgrade:testUpgradeToOrdered() (gas: 56509529)
 TestICS04Upgrade:testUpgradeToUnordered() (gas: 45113829)
 TestICS04UpgradeApp:testUpgradeAuthorizationChanneNotFound() (gas: 61690)
diff --git a/contracts/clients/09-localhost/LocalhostClient.sol b/contracts/clients/09-localhost/LocalhostClient.sol
index 6162030d..1590e6d0 100644
--- a/contracts/clients/09-localhost/LocalhostClient.sol
+++ b/contracts/clients/09-localhost/LocalhostClient.sol
@@ -94,7 +94,7 @@ contract LocalhostClient is ILightClient, ILightClientErrors {
         } else if (height.revision_height > block.number) {
             revert InvalidHeightRevisionHeight();
         }
-        return uint64(block.timestamp);
+        return uint64(block.timestamp) * 1e9;
     }
 
     /**
diff --git a/contracts/core/04-channel/IBCChannelPacketSendRecv.sol b/contracts/core/04-channel/IBCChannelPacketSendRecv.sol
index 67f7cb57..deeffcf2 100644
--- a/contracts/core/04-channel/IBCChannelPacketSendRecv.sol
+++ b/contracts/core/04-channel/IBCChannelPacketSendRecv.sol
@@ -133,8 +133,8 @@ contract IBCChannelPacketSendRecv is
         {
             revert IBCChannelTimeoutPacketHeight(block.number, msg_.packet.timeoutHeight.revision_height);
         }
-        if (msg_.packet.timeoutTimestamp != 0 && block.timestamp * 1e9 >= msg_.packet.timeoutTimestamp) {
-            revert IBCChannelTimeoutPacketTimestamp(block.timestamp * 1e9, msg_.packet.timeoutTimestamp);
+        if (msg_.packet.timeoutTimestamp != 0 && hostTimestamp() >= msg_.packet.timeoutTimestamp) {
+            revert IBCChannelTimeoutPacketTimestamp(hostTimestamp(), msg_.packet.timeoutTimestamp);
         }
 
         verifyPacketCommitment(
diff --git a/contracts/core/04-channel/IBCChannelUpgrade.sol b/contracts/core/04-channel/IBCChannelUpgrade.sol
index 50edcd87..66f80852 100644
--- a/contracts/core/04-channel/IBCChannelUpgrade.sol
+++ b/contracts/core/04-channel/IBCChannelUpgrade.sol
@@ -549,7 +549,7 @@ contract IBCChannelUpgradeInitTryAck is IBCChannelUpgradeBase, IIBCChannelUpgrad
         Timeout.Data calldata timeout = msg_.counterpartyUpgrade.timeout;
         if (
             (timeout.height.revision_height != 0 && block.number >= timeout.height.revision_height)
-                || (timeout.timestamp != 0 && block.timestamp >= timeout.timestamp)
+                || (timeout.timestamp != 0 && hostTimestamp() >= timeout.timestamp)
         ) {
             restoreChannel(msg_.portId, msg_.channelId, UpgradeHandshakeError.Timeout);
             return false;
@@ -620,7 +620,7 @@ contract IBCChannelUpgradeConfirmTimeoutCancel is IBCChannelUpgradeBase, IIBCCha
         Timeout.Data calldata timeout = msg_.counterpartyUpgrade.timeout;
         if (
             (timeout.height.revision_height != 0 && block.number >= timeout.height.revision_height)
-                || (timeout.timestamp != 0 && block.timestamp >= timeout.timestamp)
+                || (timeout.timestamp != 0 && hostTimestamp() >= timeout.timestamp)
         ) {
             restoreChannel(msg_.portId, msg_.channelId, UpgradeHandshakeError.Timeout);
             return false;
diff --git a/contracts/core/24-host/IBCHost.sol b/contracts/core/24-host/IBCHost.sol
index 6e47ba83..dd7e98d1 100644
--- a/contracts/core/24-host/IBCHost.sol
+++ b/contracts/core/24-host/IBCHost.sol
@@ -10,6 +10,13 @@ contract IBCHost is IIBCHostErrors, IBCStore {
     // In ibc-solidity, the prefix is not required, but for compatibility with ibc-go this must be a non-empty value.
     bytes internal constant DEFAULT_COMMITMENT_PREFIX = bytes("ibc");
 
+    /**
+     * @dev hostTimestamp returns the current timestamp(Unix time in nanoseconds) of the host chain.
+     */
+    function hostTimestamp() internal view virtual returns (uint64) {
+        return uint64(block.timestamp) * 1e9;
+    }
+
     /**
      * @dev _getCommitmentPrefix returns the prefix of the commitment proof.
      */
diff --git a/tests/foundry/src/ICS04Upgrade.t.sol b/tests/foundry/src/ICS04Upgrade.t.sol
index 6a1ac9f4..96389f24 100644
--- a/tests/foundry/src/ICS04Upgrade.t.sol
+++ b/tests/foundry/src/ICS04Upgrade.t.sol
@@ -2,13 +2,13 @@
 pragma solidity ^0.8.20;
 
 import "./helpers/IBCTestHelper.t.sol";
-import {Vm} from "forge-std/Test.sol";
+import {Vm, console2} from "forge-std/Test.sol";
 import {Strings} from "@openzeppelin/contracts/utils/Strings.sol";
 import {Upgrade, UpgradeFields, Timeout} from "../../../contracts/proto/Channel.sol";
 import {LocalhostClientLib} from "../../../contracts/clients/09-localhost/LocalhostClient.sol";
 import {LocalhostHelper} from "../../../contracts/clients/09-localhost/LocalhostHelper.sol";
 import {IIBCChannelRecvPacket, IIBCChannelAcknowledgePacket} from "../../../contracts/core/04-channel/IIBCChannel.sol";
-import {IIBCChannelUpgrade, IIBCChannelUpgradeBase} from "../../../contracts/core/04-channel/IIBCChannelUpgrade.sol";
+import {IIBCChannelUpgradeBase} from "../../../contracts/core/04-channel/IIBCChannelUpgrade.sol";
 import {TestIBCChannelUpgradableMockApp} from "./helpers/TestIBCChannelUpgradableMockApp.t.sol";
 import {ICS04UpgradeTestHelper} from "./helpers/ICS04UpgradeTestHelper.t.sol";
 import {ICS04PacketEventTestHelper} from "./helpers/ICS04PacketTestHelper.t.sol";
@@ -412,8 +412,8 @@ contract TestICS04Upgrade is ICS04UpgradeTestHelper, ICS04PacketEventTestHelper
 
         Timeout.Data[3] memory timeouts = [
             Timeout.Data({height: H(block.number), timestamp: 0}),
-            Timeout.Data({height: H(0), timestamp: uint64(block.timestamp)}),
-            Timeout.Data({height: H(block.number), timestamp: uint64(block.timestamp)})
+            Timeout.Data({height: H(0), timestamp: getTimestamp(0)}),
+            Timeout.Data({height: H(block.number), timestamp: getTimestamp()})
         ];
         HandshakeCallbacks memory callbacks = emptyCallbacks();
         callbacks.openInitAndFlushing.callback = _testUpgradeTimeoutAbortAck;
@@ -457,8 +457,8 @@ contract TestICS04Upgrade is ICS04UpgradeTestHelper, ICS04PacketEventTestHelper
 
         Timeout.Data[3] memory timeouts = [
             Timeout.Data({height: H(block.number), timestamp: 0}),
-            Timeout.Data({height: H(0), timestamp: uint64(block.timestamp)}),
-            Timeout.Data({height: H(block.number), timestamp: uint64(block.timestamp)})
+            Timeout.Data({height: H(0), timestamp: getTimestamp()}),
+            Timeout.Data({height: H(block.number), timestamp: getTimestamp()})
         ];
         HandshakeCallbacks memory callbacks = emptyCallbacks();
         callbacks.flushingAndFlushing.callback = _testUpgradeTimeoutAbortConfirm;
@@ -497,7 +497,7 @@ contract TestICS04Upgrade is ICS04UpgradeTestHelper, ICS04PacketEventTestHelper
     }
 
     function testUpgradeTimeoutUpgrade() public {
-        CallbacksTimeout[] memory cases = new CallbacksTimeout[](10);
+        CallbacksTimeout[] memory cases = new CallbacksTimeout[](16);
         for (uint256 i = 0; i < cases.length; i++) {
             cases[i].callbacks = emptyCallbacks();
         }
@@ -511,8 +511,8 @@ contract TestICS04Upgrade is ICS04UpgradeTestHelper, ICS04PacketEventTestHelper
         i++;
 
         cases[i].callbacks.flushingAndFlushing.callback = _testUpgradeTimeoutUpgradeSuccess;
-        cases[i].t0 = Timeout.Data({height: H(0), timestamp: uint64(block.timestamp + 1)});
-        cases[i].t1 = Timeout.Data({height: H(0), timestamp: uint64(block.timestamp + 1)});
+        cases[i].t0 = Timeout.Data({height: H(0), timestamp: getTimestamp(1)});
+        cases[i].t1 = Timeout.Data({height: H(0), timestamp: getTimestamp(1)});
         i++;
 
         cases[i].callbacks.openInitAndFlushing.callback = _testUpgradeTimeoutUpgradeSuccess;
@@ -521,22 +521,34 @@ contract TestICS04Upgrade is ICS04UpgradeTestHelper, ICS04PacketEventTestHelper
         cases[i].t1 = Timeout.Data({height: H(block.number + 1), timestamp: 0});
         i++;
 
+        cases[i].callbacks.openInitAndFlushing.callback = _testUpgradeTimeoutUpgradeSuccess;
+        cases[i].callbacks.openInitAndFlushing.reverse = true;
+        cases[i].t0 = Timeout.Data({height: H(0), timestamp: getTimestamp(1)});
+        cases[i].t1 = Timeout.Data({height: H(0), timestamp: getTimestamp(1)});
+        i++;
+
         cases[i].callbacks.flushingAndComplete.callback = _testUpgradeTimeoutUpgradeSuccess;
         cases[i].callbacks.flushingAndComplete.reverse = true;
         cases[i].t0 = Timeout.Data({height: H(block.number + 1), timestamp: 0});
         cases[i].t1 = Timeout.Data({height: H(block.number + 1), timestamp: 0});
         i++;
 
+        cases[i].callbacks.flushingAndComplete.callback = _testUpgradeTimeoutUpgradeSuccess;
+        cases[i].callbacks.flushingAndComplete.reverse = true;
+        cases[i].t0 = Timeout.Data({height: H(0), timestamp: getTimestamp(1)});
+        cases[i].t1 = Timeout.Data({height: H(0), timestamp: getTimestamp(1)});
+        i++;
+
         // ------------------------------ Failure Cases ------------------------------ //
 
-        cases[i].callbacks.flushingAndFlushing.callback = _testUpgradeTimeoutUpgradeFailNotReached;
+        cases[i].callbacks.flushingAndFlushing.callback = _testUpgradeTimeoutUpgradeFailTimeoutHeightNotReached;
         cases[i].t0 = Timeout.Data({height: H(block.number + 1), timestamp: 0});
         cases[i].t1 = Timeout.Data({height: H(block.number + 1), timestamp: 0});
         i++;
 
-        cases[i].callbacks.flushingAndFlushing.callback = _testUpgradeTimeoutUpgradeFailNotReached;
-        cases[i].t0 = Timeout.Data({height: H(0), timestamp: uint64(block.timestamp + 1)});
-        cases[i].t1 = Timeout.Data({height: H(0), timestamp: uint64(block.timestamp + 1)});
+        cases[i].callbacks.flushingAndFlushing.callback = _testUpgradeTimeoutUpgradeFailTimeoutTimestampNotReached;
+        cases[i].t0 = Timeout.Data({height: H(0), timestamp: getTimestamp(1)});
+        cases[i].t1 = Timeout.Data({height: H(0), timestamp: getTimestamp(1)});
         i++;
 
         cases[i].callbacks.flushingAndComplete.callback = _testUpgradeTimeoutUpgradeFailReached;
@@ -544,27 +556,50 @@ contract TestICS04Upgrade is ICS04UpgradeTestHelper, ICS04PacketEventTestHelper
         cases[i].t1 = Timeout.Data({height: H(block.number + 1), timestamp: 0});
         i++;
 
+        cases[i].callbacks.flushingAndComplete.callback = _testUpgradeTimeoutUpgradeFailReached;
+        cases[i].t0 = Timeout.Data({height: H(0), timestamp: getTimestamp(1)});
+        cases[i].t1 = Timeout.Data({height: H(0), timestamp: getTimestamp(1)});
+        i++;
+
         cases[i].callbacks.openSucAndComplete.callback = _testUpgradeTimeoutUpgradeFailReachedAlreadyUpgraded;
         cases[i].callbacks.openSucAndComplete.reverse = true;
         cases[i].t0 = Timeout.Data({height: H(block.number + 1), timestamp: 0});
         cases[i].t1 = Timeout.Data({height: H(block.number + 1), timestamp: 0});
         i++;
 
+        cases[i].callbacks.openSucAndComplete.callback = _testUpgradeTimeoutUpgradeFailReachedAlreadyUpgraded;
+        cases[i].callbacks.openSucAndComplete.reverse = true;
+        cases[i].t0 = Timeout.Data({height: H(0), timestamp: getTimestamp(1)});
+        cases[i].t1 = Timeout.Data({height: H(0), timestamp: getTimestamp(1)});
+        i++;
+
         cases[i].callbacks.completeAndComplete.callback = _testUpgradeTimeoutUpgradeFailReachedAlreadyCompleted;
         cases[i].t0 = Timeout.Data({height: H(block.number + 1), timestamp: 0});
         cases[i].t1 = Timeout.Data({height: H(block.number + 1), timestamp: 0});
         i++;
 
+        cases[i].callbacks.completeAndComplete.callback = _testUpgradeTimeoutUpgradeFailReachedAlreadyCompleted;
+        cases[i].t0 = Timeout.Data({height: H(0), timestamp: getTimestamp(1)});
+        cases[i].t1 = Timeout.Data({height: H(0), timestamp: getTimestamp(1)});
+        i++;
+
         cases[i].callbacks.completeAndComplete.callback = _testUpgradeTimeoutUpgradeFailReachedAlreadyCompleted;
         cases[i].callbacks.completeAndComplete.reverse = true;
         cases[i].t0 = Timeout.Data({height: H(block.number + 1), timestamp: 0});
         cases[i].t1 = Timeout.Data({height: H(block.number + 1), timestamp: 0});
         i++;
 
+        cases[i].callbacks.completeAndComplete.callback = _testUpgradeTimeoutUpgradeFailReachedAlreadyCompleted;
+        cases[i].callbacks.completeAndComplete.reverse = true;
+        cases[i].t0 = Timeout.Data({height: H(0), timestamp: getTimestamp(1)});
+        cases[i].t1 = Timeout.Data({height: H(0), timestamp: getTimestamp(1)});
+        i++;
+
         require(i == cases.length, "invalid number of cases");
 
         for (uint256 i = 0; i < cases.length; i++) {
-            (uint256 height, uint256 timestamp) = (block.number, block.timestamp);
+            console2.log("case:", i);
+            (uint256 height, uint256 timestampSec) = (block.number, block.timestamp);
             (ChannelInfo memory channel0, ChannelInfo memory channel1) =
                 createMockAppLocalhostChannel(Channel.Order.ORDER_UNORDERED);
             handshakeUpgradeWithCallbacks(
@@ -589,7 +624,7 @@ contract TestICS04Upgrade is ICS04UpgradeTestHelper, ICS04PacketEventTestHelper
             );
             // restore the block height and timestamp
             vm.roll(height);
-            vm.warp(timestamp);
+            vm.warp(timestampSec);
         }
     }
 
@@ -1822,7 +1857,7 @@ contract TestICS04Upgrade is ICS04UpgradeTestHelper, ICS04PacketEventTestHelper
             vm.roll(uint256(timeout.height.revision_height));
         }
         if (timeout.timestamp != 0) {
-            vm.warp(uint256(timeout.timestamp));
+            vm.warp(uint256(timeout.timestamp / 1e9));
         }
         (Channel.Data memory counterpartyChannel,) = handler.getChannel(channel1.portId, channel1.channelId);
         handler.timeoutChannelUpgrade(
@@ -1848,7 +1883,7 @@ contract TestICS04Upgrade is ICS04UpgradeTestHelper, ICS04PacketEventTestHelper
         return false;
     }
 
-    function _testUpgradeTimeoutUpgradeFailNotReached(
+    function _testUpgradeTimeoutUpgradeFailTimeoutHeightNotReached(
         IIBCHandler handler,
         ChannelInfo memory channel0,
         ChannelInfo memory channel1
@@ -1861,8 +1896,25 @@ contract TestICS04Upgrade is ICS04UpgradeTestHelper, ICS04PacketEventTestHelper
             proofChannel: LocalhostClientLib.sentinelProof(),
             proofHeight: H(block.number)
         });
-        // IBCChannelUpgradeTimeoutHeightNotReached or IBCChannelUpgradeTimeoutTimestampNotReached
-        vm.expectRevert();
+        vm.expectRevert(IIBCChannelUpgradeErrors.IBCChannelUpgradeTimeoutHeightNotReached.selector);
+        handler.timeoutChannelUpgrade(msg_);
+        return true;
+    }
+
+    function _testUpgradeTimeoutUpgradeFailTimeoutTimestampNotReached(
+        IIBCHandler handler,
+        ChannelInfo memory channel0,
+        ChannelInfo memory channel1
+    ) internal returns (bool) {
+        (Channel.Data memory counterpartyChannel,) = handler.getChannel(channel1.portId, channel1.channelId);
+        IIBCChannelUpgradeBase.MsgTimeoutChannelUpgrade memory msg_ = IIBCChannelUpgradeBase.MsgTimeoutChannelUpgrade({
+            portId: channel0.portId,
+            channelId: channel0.channelId,
+            counterpartyChannel: counterpartyChannel,
+            proofChannel: LocalhostClientLib.sentinelProof(),
+            proofHeight: H(block.number)
+        });
+        vm.expectRevert(IIBCChannelUpgradeErrors.IBCChannelUpgradeTimeoutTimestampNotReached.selector);
         handler.timeoutChannelUpgrade(msg_);
         return true;
     }
@@ -1877,7 +1929,7 @@ contract TestICS04Upgrade is ICS04UpgradeTestHelper, ICS04PacketEventTestHelper
             vm.roll(uint256(timeout.height.revision_height));
         }
         if (timeout.timestamp != 0) {
-            vm.warp(uint256(timeout.timestamp));
+            vm.warp(uint256(timeout.timestamp / 1e9));
         }
         (Channel.Data memory counterpartyChannel,) = handler.getChannel(channel1.portId, channel1.channelId);
         IIBCChannelUpgradeBase.MsgTimeoutChannelUpgrade memory msg_ = IIBCChannelUpgradeBase.MsgTimeoutChannelUpgrade({
@@ -1923,7 +1975,7 @@ contract TestICS04Upgrade is ICS04UpgradeTestHelper, ICS04PacketEventTestHelper
             vm.roll(uint256(timeout.height.revision_height));
         }
         if (timeout.timestamp != 0) {
-            vm.warp(uint256(timeout.timestamp));
+            vm.warp(uint256(timeout.timestamp / 1e9));
         }
         (Channel.Data memory counterpartyChannel,) = handler.getChannel(channel1.portId, channel1.channelId);
         IIBCChannelUpgradeBase.MsgTimeoutChannelUpgrade memory msg_ = IIBCChannelUpgradeBase.MsgTimeoutChannelUpgrade({
diff --git a/tests/foundry/src/helpers/IBCTestHelper.t.sol b/tests/foundry/src/helpers/IBCTestHelper.t.sol
index 1cbb4c31..f296957c 100644
--- a/tests/foundry/src/helpers/IBCTestHelper.t.sol
+++ b/tests/foundry/src/helpers/IBCTestHelper.t.sol
@@ -44,6 +44,15 @@ abstract contract IBCTestHelper is Test {
         return H(0, revisionHeight);
     }
 
+    function getTimestamp() internal returns (uint64) {
+        return getTimestamp(0);
+    }
+
+    function getTimestamp(int256 offsetSecs) internal returns (uint64) {
+        assertTrue(int256(block.timestamp) + offsetSecs >= 0, "getTimestamp: negative timestamp");
+        return uint64(uint256((int256(block.timestamp) + offsetSecs) * 1e9));
+    }
+
     function roll(uint256 bn) internal {
         require(prevBlockNumber == 0, "roll: already rolled");
         prevBlockNumber = block.number;