diff --git a/aws/smithy-aws-apigateway-openapi/src/test/resources/software/amazon/smithy/aws/apigateway/openapi/cors-model.openapi.json b/aws/smithy-aws-apigateway-openapi/src/test/resources/software/amazon/smithy/aws/apigateway/openapi/cors-model.openapi.json
index 644dbadb4df..7b04f290464 100644
--- a/aws/smithy-aws-apigateway-openapi/src/test/resources/software/amazon/smithy/aws/apigateway/openapi/cors-model.openapi.json
+++ b/aws/smithy-aws-apigateway-openapi/src/test/resources/software/amazon/smithy/aws/apigateway/openapi/cors-model.openapi.json
@@ -365,8 +365,7 @@
         "type": "object",
         "properties": {
           "createdAt": {
-            "type": "string",
-            "format": "date-time"
+            "type": "number"
           },
           "id": {
             "type": "string"
diff --git a/smithy-openapi/src/main/java/software/amazon/smithy/openapi/fromsmithy/protocols/AwsRestJsonProtocol.java b/smithy-openapi/src/main/java/software/amazon/smithy/openapi/fromsmithy/protocols/AwsRestJsonProtocol.java
index 5914c93af58..66c63c5e443 100644
--- a/smithy-openapi/src/main/java/software/amazon/smithy/openapi/fromsmithy/protocols/AwsRestJsonProtocol.java
+++ b/smithy-openapi/src/main/java/software/amazon/smithy/openapi/fromsmithy/protocols/AwsRestJsonProtocol.java
@@ -26,6 +26,7 @@
 import software.amazon.smithy.model.shapes.ShapeId;
 import software.amazon.smithy.model.shapes.ShapeIndex;
 import software.amazon.smithy.model.shapes.StructureShape;
+import software.amazon.smithy.model.traits.TimestampFormatTrait;
 import software.amazon.smithy.openapi.OpenApiConstants;
 import software.amazon.smithy.openapi.fromsmithy.Context;
 import software.amazon.smithy.utils.SetUtils;
@@ -42,7 +43,9 @@ public Set<String> getProtocolNames() {
 
     @Override
     public ObjectNode getDefaultSettings() {
-        return Node.objectNode().withMember(JsonSchemaConstants.SMITHY_USE_JSON_NAME, true);
+        return Node.objectNode()
+                .withMember(JsonSchemaConstants.SMITHY_USE_JSON_NAME, true)
+                .withMember(JsonSchemaConstants.SMITHY_DEFAULT_TIMESTAMP_FORMAT, TimestampFormatTrait.EPOCH_SECONDS);
     }
 
     @Override
diff --git a/smithy-openapi/src/test/resources/software/amazon/smithy/openapi/fromsmithy/test-service.openapi.json b/smithy-openapi/src/test/resources/software/amazon/smithy/openapi/fromsmithy/test-service.openapi.json
index 06f8220227c..3d8ab468e92 100644
--- a/smithy-openapi/src/test/resources/software/amazon/smithy/openapi/fromsmithy/test-service.openapi.json
+++ b/smithy-openapi/src/test/resources/software/amazon/smithy/openapi/fromsmithy/test-service.openapi.json
@@ -72,8 +72,7 @@
                       "type": "string"
                     },
                     "time": {
-                      "type": "string",
-                      "format": "date-time"
+                      "type": "number"
                     },
                     "list": {
                       "type": "array",
diff --git a/smithy-openapi/src/test/resources/software/amazon/smithy/openapi/fromsmithy/test-service.openapi.not-inlined.json b/smithy-openapi/src/test/resources/software/amazon/smithy/openapi/fromsmithy/test-service.openapi.not-inlined.json
index 64fdfa6a005..ace51745c06 100644
--- a/smithy-openapi/src/test/resources/software/amazon/smithy/openapi/fromsmithy/test-service.openapi.not-inlined.json
+++ b/smithy-openapi/src/test/resources/software/amazon/smithy/openapi/fromsmithy/test-service.openapi.not-inlined.json
@@ -245,8 +245,7 @@
         "type": "string"
       },
       "ExampleRestCreateDocumentOutputTimeMember": {
-        "type": "string",
-        "format": "date-time"
+        "type": "number"
       },
       "ExampleRestPutPayloadInputQueryMember": {
         "type": "number",