diff --git a/wsme/restjson.py b/wsme/restjson.py
index 771c790..1deecfb 100644
--- a/wsme/restjson.py
+++ b/wsme/restjson.py
@@ -1,4 +1,7 @@
 import base64
+import datetime
+
+from simplegeneric import generic
 
 from wsme.rest import RestProtocol
 from wsme.controller import register_protocol
@@ -10,18 +13,33 @@ except ImportError:
     import json
 
 
-def prepare_encode(value, datatype):
-    if datatype in wsme.types.pod_types:
-        return value
+@generic
+def tojson(datatype, value):
     if wsme.types.isstructured(datatype):
         d = dict()
         for name, attr in wsme.types.list_attributes(datatype):
-            d[name] = prepare_encode(getattr(value, name), attr.datatype)
+            d[name] = tojson(attr.datatype, getattr(value, name))
         return d
-    if datatype in wsme.types.dt_types:
-        return value.isoformat()
-    if datatype is wsme.types.binary:
-        return base64.encode()
+    return value
+
+
+@tojson.when_object(datetime.date)
+def date_tojson(datatype, value):
+    return value.isoformat()
+
+
+@tojson.when_object(datetime.time)
+def time_tojson(datatype, value):
+    return value.isoformat()
+
+@tojson.when_object(datetime.datetime)
+def datetime_tojson(datatype, value):
+    return value.isoformat()
+
+
+@tojson.when_object(wsme.types.binary)
+def datetime_tojson(datatype, value):
+    return base64.encode(value)
 
 
 class RestJsonProtocol(RestProtocol):
@@ -34,7 +52,7 @@ class RestJsonProtocol(RestProtocol):
         return kw
 
     def encode_result(self, result, return_type):
-        return json.dumps({'result': prepare_encode(result, return_type)})
+        return json.dumps({'result': tojson(return_type, result)})
 
     def encode_error(self, errordetail):
         return json.dumps(errordetail)