diff --git a/apps/protoc-gen-openapi/examples/google/example/library/v1/library.proto b/apps/protoc-gen-openapi/examples/google/example/library/v1/library.proto
index 80912cf..87a13a1 100644
--- a/apps/protoc-gen-openapi/examples/google/example/library/v1/library.proto
+++ b/apps/protoc-gen-openapi/examples/google/example/library/v1/library.proto
@@ -22,6 +22,7 @@ import "google/api/client.proto";
 import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/empty.proto";
+import "google/protobuf/timestamp.proto";
 
 option go_package = "google.golang.org/genproto/googleapis/example/library/v1;library";
 option java_multiple_files = true;
@@ -165,6 +166,14 @@ message Book {
 
   // Value indicating whether the book has been read.
   bool read = 4;
+
+  // Creation timestamp.
+  google.protobuf.Timestamp create_time = 5
+   [(google.api.field_behavior) = OUTPUT_ONLY];
+
+  // Last update timestamp.
+  google.protobuf.Timestamp update_time = 6
+   [(google.api.field_behavior) = OUTPUT_ONLY];
 }
 
 // A Shelf contains a collection of books with a theme.
@@ -183,6 +192,15 @@ message Shelf {
 
   // The theme of the shelf
   string theme = 2;
+
+  // Creation timestamp.
+  google.protobuf.Timestamp create_time = 3
+    [(google.api.field_behavior) = OUTPUT_ONLY];
+
+  // Last update timestamp.
+  google.protobuf.Timestamp update_time = 4
+    [(google.api.field_behavior) = OUTPUT_ONLY];
+
 }
 
 // Request message for LibraryService.CreateShelf.
diff --git a/apps/protoc-gen-openapi/examples/google/example/library/v1/openapi.yaml b/apps/protoc-gen-openapi/examples/google/example/library/v1/openapi.yaml
index 3a47552..7bd08ea 100644
--- a/apps/protoc-gen-openapi/examples/google/example/library/v1/openapi.yaml
+++ b/apps/protoc-gen-openapi/examples/google/example/library/v1/openapi.yaml
@@ -282,6 +282,16 @@ components:
                 read:
                     type: boolean
                     description: Value indicating whether the book has been read.
+                create_time:
+                    readOnly: true
+                    type: string
+                    description: Creation timestamp.
+                    format: RFC3339
+                update_time:
+                    readOnly: true
+                    type: string
+                    description: Last update timestamp.
+                    format: RFC3339
             description: A single book in the library.
         Empty:
             properties: {}
@@ -334,4 +344,14 @@ components:
                 theme:
                     type: string
                     description: The theme of the shelf
+                create_time:
+                    readOnly: true
+                    type: string
+                    description: Creation timestamp.
+                    format: RFC3339
+                update_time:
+                    readOnly: true
+                    type: string
+                    description: Last update timestamp.
+                    format: RFC3339
             description: A Shelf contains a collection of books with a theme.
diff --git a/apps/protoc-gen-openapi/generator/openapi-v3.go b/apps/protoc-gen-openapi/generator/openapi-v3.go
index 74757ef..03509d5 100644
--- a/apps/protoc-gen-openapi/generator/openapi-v3.go
+++ b/apps/protoc-gen-openapi/generator/openapi-v3.go
@@ -469,8 +469,15 @@ func (g *OpenAPIv3Generator) addSchemasToDocumentV3(d *v3.Document, file *protog
 				k := field.Desc.Kind()
 				switch k {
 				case protoreflect.MessageKind:
-					// The field is described by a reference.
-					XRef = g.schemaReferenceForTypeName(fullMessageTypeName(field.Message))
+					typeName := fullMessageTypeName(field.Message)
+					if typeName == ".google.protobuf.Timestamp" {
+						// Timestamps are serialized as strings
+						fieldSchema.Type = "string"
+						fieldSchema.Format = "RFC3339"
+					} else {
+						// The field is described by a reference.
+						XRef = g.schemaReferenceForTypeName(typeName)
+					}
 				case protoreflect.StringKind:
 					fieldSchema.Type = "string"
 				case protoreflect.Int32Kind,