diff --git a/ethereum/statetransition/src/main/java/tech/pegasys/teku/statetransition/util/DebugDataDumper.java b/ethereum/statetransition/src/main/java/tech/pegasys/teku/statetransition/util/DebugDataDumper.java
index 6790a91999f..c160c936c03 100644
--- a/ethereum/statetransition/src/main/java/tech/pegasys/teku/statetransition/util/DebugDataDumper.java
+++ b/ethereum/statetransition/src/main/java/tech/pegasys/teku/statetransition/util/DebugDataDumper.java
@@ -18,6 +18,10 @@
 import java.nio.file.Files;
 import java.nio.file.NoSuchFileException;
 import java.nio.file.Path;
+import java.sql.Date;
+import java.text.DateFormat;
+import java.text.SimpleDateFormat;
+import java.util.Optional;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 import org.apache.tuweni.bytes.Bytes;
@@ -54,11 +58,11 @@ public DebugDataDumper(final Path directory, final boolean enabled) {
   }
 
   public void saveGossipMessageDecodingError(
-      final String topic, final String arrivalTimestamp, final Bytes originalMessage) {
+      final String topic, final Optional<UInt64> arrivalTimestamp, final Bytes originalMessage) {
     if (!enabled) {
       return;
     }
-    final String fileName = String.format("%s.ssz", arrivalTimestamp);
+    final String fileName = String.format("%s.ssz", formatTimestamp(arrivalTimestamp));
     final Path topicPath =
         Path.of(GOSSIP_MESSAGES_DIR).resolve(DECODING_ERROR_SUB_DIR).resolve(topic);
     saveBytesToFile(
@@ -66,11 +70,11 @@ public void saveGossipMessageDecodingError(
   }
 
   public void saveGossipRejectedMessageToFile(
-      final String topic, final String arrivalTimestamp, final Bytes decodedMessage) {
+      final String topic, final Optional<UInt64> arrivalTimestamp, final Bytes decodedMessage) {
     if (!enabled) {
       return;
     }
-    final String fileName = String.format("%s.ssz", arrivalTimestamp);
+    final String fileName = String.format("%s.ssz", formatTimestamp(arrivalTimestamp));
     final Path topicPath = Path.of(GOSSIP_MESSAGES_DIR).resolve(REJECTED_SUB_DIR).resolve(topic);
     saveBytesToFile("rejected gossip message", topicPath.resolve(fileName), decodedMessage);
   }
@@ -135,6 +139,17 @@ private void createDirectory(final Path path, final String directoryName, final
     }
   }
 
+  @VisibleForTesting
+  protected static String formatTimestamp(final Optional<UInt64> arrivalTimestamp) {
+    if (arrivalTimestamp.isEmpty()) {
+      return "unknown";
+    }
+
+    final DateFormat df = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SS");
+    Date date = new Date(arrivalTimestamp.get().longValue());
+    return df.format(date);
+  }
+
   @VisibleForTesting
   protected boolean isEnabled() {
     return enabled;
diff --git a/ethereum/statetransition/src/main/java/tech/pegasys/teku/statetransition/util/noop/NoOpDebugDataDumper.java b/ethereum/statetransition/src/main/java/tech/pegasys/teku/statetransition/util/noop/NoOpDebugDataDumper.java
index cdd21d711d2..32c506997e4 100644
--- a/ethereum/statetransition/src/main/java/tech/pegasys/teku/statetransition/util/noop/NoOpDebugDataDumper.java
+++ b/ethereum/statetransition/src/main/java/tech/pegasys/teku/statetransition/util/noop/NoOpDebugDataDumper.java
@@ -14,6 +14,7 @@
 package tech.pegasys.teku.statetransition.util.noop;
 
 import java.nio.file.Path;
+import java.util.Optional;
 import org.apache.tuweni.bytes.Bytes;
 import org.apache.tuweni.bytes.Bytes32;
 import tech.pegasys.teku.infrastructure.unsigned.UInt64;
@@ -27,11 +28,11 @@ public NoOpDebugDataDumper() {
 
   @Override
   public void saveGossipMessageDecodingError(
-      final String topic, final String arrivalTimestamp, final Bytes originalMessage) {}
+      final String topic, final Optional<UInt64> arrivalTimestamp, final Bytes originalMessage) {}
 
   @Override
   public void saveGossipRejectedMessageToFile(
-      final String topic, final String arrivalTimestamp, final Bytes decodedMessage) {}
+      final String topic, final Optional<UInt64> arrivalTimestamp, final Bytes decodedMessage) {}
 
   @Override
   public void saveInvalidBlockToFile(
diff --git a/ethereum/statetransition/src/test/java/tech/pegasys/teku/statetransition/util/DebugDataDumperTest.java b/ethereum/statetransition/src/test/java/tech/pegasys/teku/statetransition/util/DebugDataDumperTest.java
index 32001f66407..3fd3bcad651 100644
--- a/ethereum/statetransition/src/test/java/tech/pegasys/teku/statetransition/util/DebugDataDumperTest.java
+++ b/ethereum/statetransition/src/test/java/tech/pegasys/teku/statetransition/util/DebugDataDumperTest.java
@@ -22,12 +22,14 @@
 import java.nio.file.Files;
 import java.nio.file.NoSuchFileException;
 import java.nio.file.Path;
+import java.util.Optional;
 import org.apache.tuweni.bytes.Bytes;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.condition.DisabledOnOs;
 import org.junit.jupiter.api.condition.OS;
 import org.junit.jupiter.api.io.TempDir;
 import tech.pegasys.teku.infrastructure.time.StubTimeProvider;
+import tech.pegasys.teku.infrastructure.unsigned.UInt64;
 import tech.pegasys.teku.spec.TestSpecFactory;
 import tech.pegasys.teku.spec.datastructures.blocks.SignedBeaconBlock;
 import tech.pegasys.teku.spec.util.DataStructureUtil;
@@ -41,11 +43,12 @@ class DebugDataDumperTest {
   void saveGossipMessageDecodingError_shouldSaveToFile(@TempDir Path tempDir) {
     final DebugDataDumper manager = new DebugDataDumper(tempDir, true);
     final Bytes messageBytes = dataStructureUtil.stateBuilderPhase0().build().sszSerialize();
-    final String arrivalTimestamp = timeProvider.getTimeInMillis().toString();
+    final Optional<UInt64> arrivalTimestamp = Optional.of(timeProvider.getTimeInMillis());
     final String topic = "test_topic";
     manager.saveGossipMessageDecodingError("test_topic", arrivalTimestamp, messageBytes);
 
-    final String fileName = String.format("%s.ssz", arrivalTimestamp);
+    final String fileName =
+        String.format("%s.ssz", DebugDataDumper.formatTimestamp(arrivalTimestamp));
     final Path expectedFile =
         tempDir
             .resolve("gossip_messages")
@@ -59,11 +62,12 @@ void saveGossipMessageDecodingError_shouldSaveToFile(@TempDir Path tempDir) {
   void saveGossipMessageDecodingError_shouldNotSaveToFileWhenDisabled(@TempDir Path tempDir) {
     final DebugDataDumper manager = new DebugDataDumper(tempDir, false);
     final Bytes messageBytes = dataStructureUtil.stateBuilderPhase0().build().sszSerialize();
-    final String arrivalTimestamp = timeProvider.getTimeInMillis().toString();
+    final Optional<UInt64> arrivalTimestamp = Optional.of(timeProvider.getTimeInMillis());
     manager.saveGossipMessageDecodingError("test_topic", arrivalTimestamp, messageBytes);
     assertThat(manager.isEnabled()).isFalse();
 
-    final String fileName = String.format("%s.ssz", arrivalTimestamp);
+    final String fileName =
+        String.format("%s.ssz", DebugDataDumper.formatTimestamp(arrivalTimestamp));
     final Path expectedFile =
         tempDir.resolve("gossip_messages").resolve("decoding_error").resolve(fileName);
     checkFileNotExist(expectedFile);
@@ -73,11 +77,12 @@ void saveGossipMessageDecodingError_shouldNotSaveToFileWhenDisabled(@TempDir Pat
   void saveGossipRejectedMessageToFile_shouldSaveToFile(@TempDir Path tempDir) {
     final DebugDataDumper manager = new DebugDataDumper(tempDir, true);
     final Bytes messageBytes = dataStructureUtil.stateBuilderPhase0().build().sszSerialize();
-    final String arrivalTimestamp = timeProvider.getTimeInMillis().toString();
+    final Optional<UInt64> arrivalTimestamp = Optional.of(timeProvider.getTimeInMillis());
     final String topic = "test_topic";
     manager.saveGossipRejectedMessageToFile("test_topic", arrivalTimestamp, messageBytes);
 
-    final String fileName = String.format("%s.ssz", arrivalTimestamp);
+    final String fileName =
+        String.format("%s.ssz", DebugDataDumper.formatTimestamp(arrivalTimestamp));
     final Path expectedFile =
         tempDir.resolve("gossip_messages").resolve("rejected").resolve(topic).resolve(fileName);
     checkBytesSavedToFile(expectedFile, messageBytes);
@@ -87,7 +92,7 @@ void saveGossipRejectedMessageToFile_shouldSaveToFile(@TempDir Path tempDir) {
   void saveGossipRejectedMessageToFile_shouldNotSaveToFileWhenDisabled(@TempDir Path tempDir) {
     final DebugDataDumper manager = new DebugDataDumper(tempDir, false);
     final Bytes messageBytes = dataStructureUtil.stateBuilderPhase0().build().sszSerialize();
-    final String arrivalTimestamp = timeProvider.getTimeInMillis().toString();
+    final Optional<UInt64> arrivalTimestamp = Optional.of(timeProvider.getTimeInMillis());
     manager.saveGossipRejectedMessageToFile("test_topic", arrivalTimestamp, messageBytes);
     assertThat(manager.isEnabled()).isFalse();
 
@@ -150,6 +155,19 @@ void constructionOfDirectories_shouldDisableWhenFailedToCreate(@TempDir Path tem
     assertThat(manager.isEnabled()).isFalse();
   }
 
+  @Test
+  void formatTimestamp_shouldFormatDate() {
+    final String formattedTimestamp =
+        DebugDataDumper.formatTimestamp(Optional.of(dataStructureUtil.randomUInt64()));
+    assertThat(formattedTimestamp).isEqualTo("147882977-02-28T19:22:42.956");
+  }
+
+  @Test
+  void formatTimestamp_shouldReturnConsistentUnknown() {
+    final String formattedTimestamp = DebugDataDumper.formatTimestamp(Optional.empty());
+    assertThat(formattedTimestamp).isEqualTo("unknown");
+  }
+
   private void checkBytesSavedToFile(final Path path, final Bytes expectedBytes) {
     try {
       final Bytes bytes = Bytes.wrap(Files.readAllBytes(path));
diff --git a/networking/eth2/src/main/java/tech/pegasys/teku/networking/eth2/gossip/topics/topichandlers/Eth2TopicHandler.java b/networking/eth2/src/main/java/tech/pegasys/teku/networking/eth2/gossip/topics/topichandlers/Eth2TopicHandler.java
index d6d7c0aab10..3e57420f403 100644
--- a/networking/eth2/src/main/java/tech/pegasys/teku/networking/eth2/gossip/topics/topichandlers/Eth2TopicHandler.java
+++ b/networking/eth2/src/main/java/tech/pegasys/teku/networking/eth2/gossip/topics/topichandlers/Eth2TopicHandler.java
@@ -137,7 +137,7 @@ private void processMessage(
       case REJECT:
         debugDataDumper.saveGossipRejectedMessageToFile(
             getTopic(),
-            message.getArrivalTimestamp().map(UInt64::toString).orElse("unknown"),
+            message.getArrivalTimestamp(),
             message.getDecodedMessage().getDecodedMessage().orElse(Bytes.EMPTY));
         P2P_LOG.onGossipRejected(
             getTopic(),
@@ -171,9 +171,7 @@ protected ValidationResult handleMessageProcessingError(
     final ValidationResult response;
     if (ExceptionUtil.hasCause(err, DecodingException.class)) {
       debugDataDumper.saveGossipMessageDecodingError(
-          getTopic(),
-          message.getArrivalTimestamp().map(UInt64::toString).orElse("unknown"),
-          message.getOriginalMessage());
+          getTopic(), message.getArrivalTimestamp(), message.getOriginalMessage());
       P2P_LOG.onGossipMessageDecodingError(getTopic(), message.getOriginalMessage(), err);
       response = ValidationResult.Invalid;
     } else if (ExceptionUtil.hasCause(err, RejectedExecutionException.class)) {