diff --git a/fulfil_client/serialization.py b/fulfil_client/serialization.py
index 5c97151..1e412c5 100644
--- a/fulfil_client/serialization.py
+++ b/fulfil_client/serialization.py
@@ -3,6 +3,8 @@
 from decimal import Decimal
 from collections import namedtuple
 from functools import partial
+import isodate
+
 try:
     import simplejson as json
 except ImportError:
@@ -10,7 +12,7 @@
 import base64
 
 
-CONTENT_TYPE = 'application/vnd.fulfil.v2+json'
+CONTENT_TYPE = "application/vnd.fulfil.v3+json"
 
 
 class JSONDecoder(object):
@@ -23,69 +25,90 @@ def register(cls, klass, decoder):
         cls.decoders[klass] = decoder
 
     def __call__(self, dct):
-        if dct.get('__class__') in self.decoders:
-            return self.decoders[dct['__class__']](dct)
+        if dct.get("__class__") in self.decoders:
+            return self.decoders[dct["__class__"]](dct)
         return dct
 
 
-JSONDecoder.register(
-    'datetime',
-    lambda dct: datetime.datetime(
-        dct['year'], dct['month'], dct['day'],
-        dct['hour'], dct['minute'], dct['second'], dct['microsecond']
+def register_decoder(klass):
+    def decorator(decoder):
+        assert klass not in JSONDecoder.decoders
+        JSONDecoder.decoders[klass] = decoder
+
+    return decorator
+
+
+@register_decoder("datetime")
+def datetime_decoder(v):
+    if v.get("iso_string"):
+        return isodate.parse_datetime(v["iso_string"])
+    return datetime.datetime(
+        v["year"],
+        v["month"],
+        v["day"],
+        v["hour"],
+        v["minute"],
+        v["second"],
+        v["microsecond"],
     )
-)
-JSONDecoder.register(
-    'date',
-    lambda dct: datetime.date(dct['year'], dct['month'], dct['day'])
-)
-JSONDecoder.register(
-    'time',
-    lambda dct: datetime.time(
-        dct['hour'], dct['minute'], dct['second'], dct['microsecond']
+
+
+@register_decoder("date")
+def date_decoder(v):
+    if v.get("iso_string"):
+        return isodate.parse_date(v["iso_string"])
+    return datetime.date(
+        v["year"],
+        v["month"],
+        v["day"],
     )
-)
-JSONDecoder.register(
-    'timedelta',
-    lambda dct: datetime.timedelta(seconds=dct['seconds'])
-)
 
 
-def _bytes_decoder(dct):
+@register_decoder("time")
+def time_decoder(v):
+    if v.get("iso_string"):
+        return isodate.parse_time(v["iso_string"])
+    return datetime.time(v["hour"], v["minute"], v["second"], v["microsecond"])
+
+
+@register_decoder("timedelta")
+def timedelta_decoder(v):
+    if v.get("iso_string"):
+        return isodate.parse_duration(v["iso_string"])
+    return datetime.timedelta(seconds=v["seconds"])
+
+
+@register_decoder("bytes")
+def _bytes_decoder(v):
     cast = bytearray if bytes == str else bytes
-    return cast(base64.b64decode(dct['base64'].encode('utf-8')))
+    return cast(base64.decodebytes(v["base64"].encode("utf-8")))
 
 
-JSONDecoder.register('bytes', _bytes_decoder)
-JSONDecoder.register(
-    'Decimal', lambda dct: Decimal(dct['decimal'])
-)
+@register_decoder("Decimal")
+def decimal_decoder(v):
+    return Decimal(v["decimal"])
 
 
-dummy_record = namedtuple('Record', ['model_name', 'id', 'rec_name'])
-JSONDecoder.register(
-    'Model', lambda dct: dummy_record(
-        dct['model_name'], dct['id'], dct.get('rec_name')
-    )
-)
+dummy_record = namedtuple("Record", ["model_name", "id", "rec_name"])
+
 
+@register_decoder("Model")
+def model_decoder(dct):
+    return dummy_record(dct["model_name"], dct["id"], dct.get("rec_name"))
 
+
+@register_decoder("AsyncResult")
 def parse_async_result(dct):
     from .client import AsyncResult
-    return AsyncResult(dct['task_id'], dct['token'], None)
-
 
-JSONDecoder.register(
-    'AsyncResult', parse_async_result
-)
+    return AsyncResult(dct["task_id"], dct["token"], None)
 
 
 class JSONEncoder(json.JSONEncoder):
-
     serializers = {}
 
     def __init__(self, *args, **kwargs):
-        super(JSONEncoder, self).__init__(*args, **kwargs)
+        super().__init__(*args, **kwargs)
         # Force to use our custom decimal with simplejson
         self.use_decimal = False
 
@@ -95,63 +118,51 @@ def register(cls, klass, encoder):
         cls.serializers[klass] = encoder
 
     def default(self, obj):
-        marshaller = self.serializers.get(
-            type(obj),
-            super(JSONEncoder, self).default
-        )
+        marshaller = self.serializers.get(type(obj), super().default)
         return marshaller(obj)
 
 
 JSONEncoder.register(
     datetime.datetime,
     lambda o: {
-        '__class__': 'datetime',
-        'year': o.year,
-        'month': o.month,
-        'day': o.day,
-        'hour': o.hour,
-        'minute': o.minute,
-        'second': o.second,
-        'microsecond': o.microsecond,
-        'iso_string': o.isoformat(),
-    })
+        "__class__": "datetime",
+        "iso_string": o.isoformat(),
+    },
+)
 JSONEncoder.register(
     datetime.date,
     lambda o: {
-        '__class__': 'date',
-        'year': o.year,
-        'month': o.month,
-        'day': o.day,
-        'iso_string': o.isoformat(),
-    })
+        "__class__": "date",
+        "iso_string": o.isoformat(),
+    },
+)
 JSONEncoder.register(
     datetime.time,
     lambda o: {
-        '__class__': 'time',
-        'hour': o.hour,
-        'minute': o.minute,
-        'second': o.second,
-        'microsecond': o.microsecond,
-    })
+        "__class__": "time",
+        "iso_string": o.isoformat(),
+    },
+)
 JSONEncoder.register(
     datetime.timedelta,
     lambda o: {
-        '__class__': 'timedelta',
-        'seconds': o.total_seconds(),
-    })
-_bytes_encoder = lambda o: {
-    '__class__': 'bytes',
-    'base64': base64.encodestring(o).decode('utf-8'),
-    }
+        "__class__": "timedelta",
+        "iso_string": isodate.duration_isoformat(o),
+    },
+)
+_bytes_encoder = lambda o: {  # noqa
+    "__class__": "bytes",
+    "base64": base64.b64encode(o).decode("utf-8"),
+}
 JSONEncoder.register(bytes, _bytes_encoder)
 JSONEncoder.register(bytearray, _bytes_encoder)
 JSONEncoder.register(
     Decimal,
     lambda o: {
-        '__class__': 'Decimal',
-        'decimal': str(o),
-    })
-
+        "__class__": "Decimal",
+        "decimal": str(o),
+    },
+)
 
 
 dumps = partial(json.dumps, cls=JSONEncoder)
diff --git a/setup.py b/setup.py
index b22b499..38e2f23 100755
--- a/setup.py
+++ b/setup.py
@@ -22,6 +22,7 @@
     'babel',
     'six',
     'more-itertools',
+    'isodate',
 ]