diff --git a/docs/api-guide/fields.md b/docs/api-guide/fields.md
index 9a745cf199..028769368a 100644
--- a/docs/api-guide/fields.md
+++ b/docs/api-guide/fields.md
@@ -199,7 +199,7 @@ If you want to override this behavior, you'll need to declare the `DateTimeField
 
 **Signature:** `DateTimeField(format=None, input_formats=None)`
 
-* `format` - A string representing the output format.  If not specified, the `DATETIME_FORMAT` setting will be used, which defaults to `'iso-8601'`.
+* `format` - A string representing the output format.  If not specified, this defaults to `None`, which indicates that python `datetime` objects should be returned by `to_native`.  In this case the datetime encoding will be determined by the renderer. 
 * `input_formats` - A list of strings representing the input formats which may be used to parse the date. If not specified, the `DATETIME_INPUT_FORMATS` setting will be used, which defaults to `['iso-8601']`.
 
 DateTime format strings may either be [python strftime formats][strftime] which explicitly specifiy the format, or the special string `'iso-8601'`, which indicates that [ISO 8601][iso8601] style datetimes should be used. (eg `'2013-01-29T12:34:56.000000'`)
@@ -212,7 +212,7 @@ Corresponds to `django.db.models.fields.DateField`
 
 **Signature:** `DateField(format=None, input_formats=None)`
 
-* `format` - A string representing the output format.  If not specified, the `DATE_FORMAT` setting will be used, which defaults to `'iso-8601'`.
+* `format` - A string representing the output format.  If not specified, this defaults to `None`, which indicates that python `date` objects should be returned by `to_native`.  In this case the date encoding will be determined by the renderer.
 * `input_formats` - A list of strings representing the input formats which may be used to parse the date. If not specified, the `DATE_INPUT_FORMATS` setting will be used, which defaults to `['iso-8601']`. 
 
 Date format strings may either be [python strftime formats][strftime] which explicitly specifiy the format, or the special string `'iso-8601'`, which indicates that [ISO 8601][iso8601] style dates should be used. (eg `'2013-01-29'`)
@@ -227,7 +227,7 @@ Corresponds to `django.db.models.fields.TimeField`
 
 **Signature:** `TimeField(format=None, input_formats=None)`
 
-* `format` - A string representing the output format.  If not specified, the `TIME_FORMAT` setting will be used, which defaults to `'iso-8601'`.
+* `format` - A string representing the output format.  If not specified, this defaults to `None`, which indicates that python `time` objects should be returned by `to_native`.  In this case the time encoding will be determined by the renderer.
 * `input_formats` - A list of strings representing the input formats which may be used to parse the date. If not specified, the `TIME_INPUT_FORMATS` setting will be used, which defaults to `['iso-8601']`.
 
 Time format strings may either be [python strftime formats][strftime] which explicitly specifiy the format, or the special string `'iso-8601'`, which indicates that [ISO 8601][iso8601] style times should be used. (eg `'12:34:56.000000'`)
@@ -273,6 +273,49 @@ Django's regular [FILE_UPLOAD_HANDLERS] are used for handling uploaded files.
 
 ---
 
+# Custom fields
+
+If you want to create a custom field, you'll probably want to override either one or both of the `.to_native()` and `.from_native()` methods.  These two methods are used to convert between the intial datatype, and a primative, serializable datatype.  Primative datatypes may be any of a number, string, date/time/datetime or None.  They may also be any list or dictionary like object that only contains other primative objects.
+
+The `.to_native()` method is called to convert the initial datatype into a primative, serializable datatype.  The `from_native()` method is called to restore a primative datatype into it's initial representation.
+
+## Examples
+
+Let's look at an example of serializing a class that represents an RGB color value:
+
+    class Color(object):
+        """
+        A color represented in the RGB colorspace.
+        """
+        def __init__(self, red, green, blue):
+            assert(red >= 0 and green >= 0 and blue >= 0)
+            assert(red < 256 and green < 256 and blue < 256)
+            self.red, self.green, self.blue = red, green, blue
+
+    class ColourField(serializers.WritableField):
+        """
+        Color objects are serialized into "rgb(#, #, #)" notation.
+        """
+        def to_native(self, obj):
+            return "rgb(%d, %d, %d)" % (obj.red, obj.green, obj.blue)
+      
+        def from_native(self, data):
+            data = data.strip('rgb(').rstrip(')')
+            red, green, blue = [int(col) for col in data.split(',')]
+            return Color(red, green, blue)
+            
+
+By default field values are treated as mapping to an attribute on the object.  If you need to customize how the field value is accessed and set you need to override `.field_to_native()` and/or `.field_from_native()`.
+
+As an example, let's create a field that can be used represent the class name of the object being serialized:
+
+    class ClassNameField(serializers.Field):
+        def field_to_native(self, obj, field_name):
+            """
+            Serialize the object's class name.
+            """
+            return obj.__class__
+
 [cite]: https://docs.djangoproject.com/en/dev/ref/forms/api/#django.forms.Form.cleaned_data
 [FILE_UPLOAD_HANDLERS]: https://docs.djangoproject.com/en/dev/ref/settings/#std:setting-FILE_UPLOAD_HANDLERS
 [strftime]: http://docs.python.org/2/library/datetime.html#strftime-and-strptime-behavior
diff --git a/docs/api-guide/serializers.md b/docs/api-guide/serializers.md
index 42edf9af19..42e81cad57 100644
--- a/docs/api-guide/serializers.md
+++ b/docs/api-guide/serializers.md
@@ -37,9 +37,6 @@ Declaring a serializer looks very similar to declaring a form:
             """
             Given a dictionary of deserialized field values, either update
             an existing model instance, or create a new model instance.
-            
-            Note that if we don't define this method, then deserializing
-            data will simply return a dictionary of items.
             """
             if instance is not None:
                 instance.title = attrs.get('title', instance.title)
@@ -48,7 +45,9 @@ Declaring a serializer looks very similar to declaring a form:
                 return instance
             return Comment(**attrs) 
 
-The first part of serializer class defines the fields that get serialized/deserialized.  The `restore_object` method defines how fully fledged instances get created when deserializing data.  The `restore_object` method is optional, and is only required if we want our serializer to support deserialization.
+The first part of serializer class defines the fields that get serialized/deserialized.  The `restore_object` method defines how fully fledged instances get created when deserializing data.
+
+The `restore_object` method is optional, and is only required if we want our serializer to support deserialization into fully fledged object instances.  If we don't define this method, then deserializing data will simply return a dictionary of items.
 
 ## Serializing objects
 
@@ -88,23 +87,21 @@ By default, serializers must be passed values for all required fields or they wi
 
     serializer = CommentSerializer(comment, data={'content': u'foo bar'}, partial=True)  # Update `instance` with partial data
 
-## Serializing querysets
-
-To serialize a queryset instead of an object instance, you should pass the `many=True` flag when instantiating the serializer.
+## Validation
 
-    queryset = Comment.objects.all()
-    serializer = CommentSerializer(queryset, many=True)
-    serializer.data
-    # [{'email': u'leila@example.com', 'content': u'foo bar', 'created': datetime.datetime(2012, 8, 22, 16, 20, 9, 822774)}, {'email': u'jamie@example.com', 'content': u'baz', 'created': datetime.datetime(2013, 1, 12, 16, 12, 45, 104445)}]
+When deserializing data, you always need to call `is_valid()` before attempting to access the deserialized object.  If any validation errors occur, the `.errors` property will contain a dictionary representing the resulting error messages.  For example:
 
-## Validation
+    serializer = CommentSerializer(data={'email': 'foobar', 'content': 'baz'})
+    serializer.is_valid()
+    # False
+    serializer.errors
+    # {'email': [u'Enter a valid e-mail address.'], 'created': [u'This field is required.']}
 
-When deserializing data, you always need to call `is_valid()` before attempting to access the deserialized object.  If any validation errors occur, the `.errors` property will contain a dictionary representing the resulting error messages.
 Each key in the dictionary will be the field name, and the values will be lists of strings of any error messages corresponding to that field.  The `non_field_errors` key may also be present, and will list any general validation errors.
 
 When deserializing a list of items, errors will be returned as a list of dictionaries representing each of the deserialized items.
 
-### Field-level validation
+#### Field-level validation
 
 You can specify custom field-level validation by adding `.validate_<fieldname>` methods to your `Serializer` subclass. These are analagous to `.clean_<fieldname>` methods on Django forms, but accept slightly different arguments.
 
@@ -127,7 +124,7 @@ Your `validate_<fieldname>` methods should either just return the `attrs` dictio
                 raise serializers.ValidationError("Blog post is not about Django")
             return attrs
 
-### Object-level validation
+#### Object-level validation
 
 To do any other validation that requires access to multiple fields, add a method called `.validate()` to your `Serializer` subclass. This method takes a single argument, which is the `attrs` dictionary. It should raise a `ValidationError` if necessary, or just return `attrs`.  For example:
 
@@ -148,26 +145,44 @@ To do any other validation that requires access to multiple fields, add a method
 
 ## Saving object state
 
-Serializers also include a `.save()` method that you can override if you want to provide a method of persisting the state of a deserialized object.  The default behavior of the method is to simply call `.save()` on the deserialized object instance.
+To save the deserialized objects created by a serializer, call the `.save()` method:
+
+    if serializer.is_valid():
+        serializer.save()
+
+The default behavior of the method is to simply call `.save()` on the deserialized object instance.  You can override the default save behaviour by overriding the `.save_object(obj)` method on the serializer class.
 
 The generic views provided by REST framework call the `.save()` method when updating or creating entities.  
 
 ## Dealing with nested objects
 
-The previous example is fine for dealing with objects that only have simple datatypes, but sometimes we also need to be able to represent more complex objects,
-where some of the attributes of an object might not be simple datatypes such as strings, dates or integers.
+The previous examples are fine for dealing with objects that only have simple datatypes, but sometimes we also need to be able to represent more complex objects, where some of the attributes of an object might not be simple datatypes such as strings, dates or integers.
 
 The `Serializer` class is itself a type of `Field`, and can be used to represent relationships where one object type is nested inside another.
 
     class UserSerializer(serializers.Serializer):
-        email = serializers.Field()
-        username = serializers.Field()
+        email = serializers.EmailField()
+        username = serializers.CharField(max_length=100)
 
     class CommentSerializer(serializers.Serializer):
         user = UserSerializer()
-        title = serializers.Field()
-        content = serializers.Field()
-        created = serializers.Field()
+        content = serializers.CharField(max_length=200)
+        created = serializers.DateTimeField()
+
+If a nested representation may optionally accept the `None` value you should pass the `required=False` flag to the nested serializer.
+
+    class CommentSerializer(serializers.Serializer):
+        user = UserSerializer(required=False)  # May be an anonymous user.
+        content = serializers.CharField(max_length=200)
+        created = serializers.DateTimeField()
+
+Similarly if a nested representation should be a list of items, you should the `many=True` flag to the nested serialized.
+
+    class CommentSerializer(serializers.Serializer):
+        user = UserSerializer(required=False)
+        edits = EditItemSerializer(many=True)  # A nested list of 'edit' items.
+        content = serializers.CharField(max_length=200)
+        created = serializers.DateTimeField()
 
 ---
 
@@ -175,58 +190,107 @@ The `Serializer` class is itself a type of `Field`, and can be used to represent
 
 ---
 
-## Including extra context
+## Dealing with multiple objects
 
-There are some cases where you need to provide extra context to the serializer in addition to the object being serialized.  One common case is if you're using a serializer that includes hyperlinked relations, which requires the serializer to have access to the current request so that it can properly generate fully qualified URLs.
+The `Serializer` class can also handle serializing or deserializing lists of objects.
 
-You can provide arbitrary additional context by passing a `context` argument when instantiating the serializer. For example:
+#### Serializing multiple objects
 
-    serializer = AccountSerializer(account, context={'request': request})
+To serialize a queryset or list of objects instead of a single object instance, you should pass the `many=True` flag when instantiating the serializer.  You can then pass a queryset or list of objects to be serialized.
+
+    queryset = Book.objects.all()
+    serializer = BookSerializer(queryset, many=True)
     serializer.data
-    # {'id': 6, 'owner': u'denvercoder9', 'created': datetime.datetime(2013, 2, 12, 09, 44, 56, 678870), 'details': 'http://example.com/accounts/6/details'}
+    # [
+    #     {'id': 0, 'title': 'The electric kool-aid acid test', 'author': 'Tom Wolfe'},
+    #     {'id': 1, 'title': 'If this is a man', 'author': 'Primo Levi'},
+    #     {'id': 2, 'title': 'The wind-up bird chronicle', 'author': 'Haruki Murakami'}
+    # ]
 
-The context dictionary can be used within any serializer field logic, such as a custom `.to_native()` method, by accessing the `self.context` attribute.
+#### Deserializing multiple objects for creation
 
-## Creating custom fields
-
-If you want to create a custom field, you'll probably want to override either one or both of the `.to_native()` and `.from_native()` methods.  These two methods are used to convert between the intial datatype, and a primative, serializable datatype.  Primative datatypes may be any of a number, string, date/time/datetime or None.  They may also be any list or dictionary like object that only contains other primative objects.
-
-The `.to_native()` method is called to convert the initial datatype into a primative, serializable datatype.  The `from_native()` method is called to restore a primative datatype into it's initial representation.
-
-Let's look at an example of serializing a class that represents an RGB color value:
-
-    class Color(object):
-        """
-        A color represented in the RGB colorspace.
-        """
-        def __init__(self, red, green, blue):
-            assert(red >= 0 and green >= 0 and blue >= 0)
-            assert(red < 256 and green < 256 and blue < 256)
-            self.red, self.green, self.blue = red, green, blue
-
-    class ColourField(serializers.WritableField):
-        """
-        Color objects are serialized into "rgb(#, #, #)" notation.
-        """
-        def to_native(self, obj):
-            return "rgb(%d, %d, %d)" % (obj.red, obj.green, obj.blue)
-      
-        def from_native(self, data):
-            data = data.strip('rgb(').rstrip(')')
-            red, green, blue = [int(col) for col in data.split(',')]
-            return Color(red, green, blue)
-            
+To deserialize a list of object data, and create multiple object instances in a single pass, you should also set the `many=True` flag, and pass a list of data to be deserialized.
 
-By default field values are treated as mapping to an attribute on the object.  If you need to customize how the field value is accessed and set you need to override `.field_to_native()` and/or `.field_from_native()`.
+This allows you to write views that create multiple items when a `POST` request is made.
 
-As an example, let's create a field that can be used represent the class name of the object being serialized:
+For example:
 
-    class ClassNameField(serializers.Field):
-        def field_to_native(self, obj, field_name):
+    data = [
+        {'title': 'The bell jar', 'author': 'Sylvia Plath'},
+        {'title': 'For whom the bell tolls', 'author': 'Ernest Hemingway'}
+    ]
+    serializer = BookSerializer(data=data, many=True)
+    serializer.is_valid()
+    # True
+    serializer.save()  # `.save()` will be called on each deserialized instance
+
+#### Deserializing multiple objects for update
+
+You can also deserialize a list of objects as part of a bulk update of multiple existing items.
+In this case you need to supply both an existing list or queryset of items, as well as a list of data to update those items with.
+
+This allows you to write views that update or create multiple items when a `PUT` request is made.
+
+    # Capitalizing the titles of the books
+    queryset = Book.objects.all()
+    data = [
+        {'id': 3, 'title': 'The Bell Jar', 'author': 'Sylvia Plath'},
+        {'id': 4, 'title': 'For Whom the Bell Tolls', 'author': 'Ernest Hemingway'}
+    ]
+    serializer = BookSerializer(queryset, data=data, many=True)
+    serializer.is_valid()
+    # True
+    serialize.save()  # `.save()` will be called on each updated or newly created instance.
+
+Bulk updates will update any instances that already exist, and create new instances for data items that do not have a corresponding instance.
+
+When performing a bulk update you may want any items that are not present in the incoming data to be deleted.  To do so, pass `allow_delete=True` to the serializer.
+
+    serializer = BookSerializer(queryset, data=data, many=True, allow_delete=True)
+    serializer.is_valid()
+    # True
+    serializer.save()  # `.save()` will be called on each updated or newly created instance.
+                       # `.delete()` will be called on any other items in the `queryset`.
+
+Passing `allow_delete=True` ensures that any update operations will completely overwrite the existing queryset, rather than simply updating any objects found in the incoming data. 
+
+#### How identity is determined when performing bulk updates
+
+Performing a bulk update is slightly more complicated than performing a bulk creation, because the serializer needs a way of determining how the items in the incoming data should be matched against the existing object instances.
+
+By default the serializer class will use the `id` key on the incoming data to determine the canonical identity of an object.  If you need to change this behavior you should override the `get_identity` method on the `Serializer` class.  For example:
+
+    class AccountSerializer(serializers.Serializer):
+        slug = serializers.CharField(max_length=100)
+        created = serializers.DateTimeField()
+        ...  # Various other fields
+        
+        def get_identity(self, data):
             """
-            Serialize the object's class name.
+            This hook is required for bulk update.
+            We need to override the default, to use the slug as the identity.
+            
+            Note that the data has not yet been validated at this point,
+            so we need to deal gracefully with incorrect datatypes.
             """
-            return obj.__class__
+            try:
+                return data.get('slug', None)
+            except AttributeError:
+                return None
+
+To map the incoming data items to their corresponding object instances, the `.get_identity()` method will be called both against the incoming data, and against the serialized representation of the existing objects.
+
+## Including extra context
+
+There are some cases where you need to provide extra context to the serializer in addition to the object being serialized.  One common case is if you're using a serializer that includes hyperlinked relations, which requires the serializer to have access to the current request so that it can properly generate fully qualified URLs.
+
+You can provide arbitrary additional context by passing a `context` argument when instantiating the serializer. For example:
+
+    serializer = AccountSerializer(account, context={'request': request})
+    serializer.data
+    # {'id': 6, 'owner': u'denvercoder9', 'created': datetime.datetime(2013, 2, 12, 09, 44, 56, 678870), 'details': 'http://example.com/accounts/6/details'}
+
+The context dictionary can be used within any serializer field logic, such as a custom `.to_native()` method, by accessing the `self.context` attribute.
 
 ---
 
diff --git a/docs/api-guide/settings.md b/docs/api-guide/settings.md
index 1163869695..c0d8d9eea1 100644
--- a/docs/api-guide/settings.md
+++ b/docs/api-guide/settings.md
@@ -192,44 +192,56 @@ Default: `'format'`
 
 ---
 
-## Date/Time formatting
+## Date and time formatting
 
 *The following settings are used to control how date and time representations may be parsed and rendered.*
 
 #### DATETIME_FORMAT
 
-A format string that should be used by default for rendering the output of `DateTimeField` serializer fields.
+A format string that should be used by default for rendering the output of `DateTimeField` serializer fields.  If `None`, then `DateTimeField` serializer fields will return python `datetime` objects, and the datetime encoding will be determined by the renderer.
 
-Default: `'iso-8601'`
+May be any of `None`, `'iso-8601'` or a python [strftime format][strftime] string.
+
+Default: `None'`
 
 #### DATETIME_INPUT_FORMATS
 
 A list of format strings that should be used by default for parsing inputs to `DateTimeField` serializer fields.
 
+May be a list including the string `'iso-8601'` or python [strftime format][strftime] strings.
+
 Default: `['iso-8601']`
 
 #### DATE_FORMAT
 
-A format string that should be used by default for rendering the output of `DateField` serializer fields.
+A format string that should be used by default for rendering the output of `DateField` serializer fields.  If `None`, then `DateField` serializer fields will return python `date` objects, and the date encoding will be determined by the renderer.
 
-Default: `'iso-8601'`
+May be any of `None`, `'iso-8601'` or a python [strftime format][strftime] string.
+
+Default: `None`
 
 #### DATE_INPUT_FORMATS
 
 A list of format strings that should be used by default for parsing inputs to `DateField` serializer fields.
 
+May be a list including the string `'iso-8601'` or python [strftime format][strftime] strings.
+
 Default: `['iso-8601']`
 
 #### TIME_FORMAT
 
-A format string that should be used by default for rendering the output of `TimeField` serializer fields.
+A format string that should be used by default for rendering the output of `TimeField` serializer fields.  If `None`, then `TimeField` serializer fields will return python `time` objects, and the time encoding will be determined by the renderer.
+
+May be any of `None`, `'iso-8601'` or a python [strftime format][strftime] string.
 
-Default: `'iso-8601'`
+Default: `None`
 
 #### TIME_INPUT_FORMATS
 
 A list of format strings that should be used by default for parsing inputs to `TimeField` serializer fields.
 
+May be a list including the string `'iso-8601'` or python [strftime format][strftime] strings.
+
 Default: `['iso-8601']`
 
 ---
@@ -243,3 +255,4 @@ The name of a parameter in the URL conf that may be used to provide a format suf
 Default: `'format'`
 
 [cite]: http://www.python.org/dev/peps/pep-0020/
+[strftime]: http://docs.python.org/2/library/time.html#time.strftime
\ No newline at end of file
diff --git a/docs/topics/release-notes.md b/docs/topics/release-notes.md
index c45fff8808..f506c610f3 100644
--- a/docs/topics/release-notes.md
+++ b/docs/topics/release-notes.md
@@ -42,6 +42,8 @@ You can determine your currently installed version using `pip freeze`:
 
 ### Master
 
+* Regression fix: Date and time fields return date/time objects by default.  Fixes regressions caused by 2.2.2.  See [#743][743] for more details.
+* Bugfix: Fix 500 error is OAuth not attempted with OAuthAuthentication class installed.
 * `Serializer.save()` now supports arbitrary keyword args which are passed through to the object `.save()` method.  Mixins use `force_insert` and `force_update` where appropriate, resulting in one less database query.
 
 ### 2.2.4
@@ -434,6 +436,7 @@ This change will not affect user code, so long as it's following the recommended
 [django-deprecation-policy]: https://docs.djangoproject.com/en/dev/internals/release-process/#internal-release-deprecation-policy
 [defusedxml-announce]: http://blog.python.org/2013/02/announcing-defusedxml-fixes-for-xml.html
 [2.2-announcement]: 2.2-announcement.md
+[743]: https://github.com/tomchristie/django-rest-framework/pull/743
 [staticfiles14]: https://docs.djangoproject.com/en/1.4/howto/static-files/#with-a-template-tag
 [staticfiles13]: https://docs.djangoproject.com/en/1.3/howto/static-files/#with-a-template-tag
 [2.1.0-notes]: https://groups.google.com/d/topic/django-rest-framework/Vv2M0CMY9bg/discussion
diff --git a/rest_framework/authentication.py b/rest_framework/authentication.py
index b4b73699eb..8f4ec536ee 100644
--- a/rest_framework/authentication.py
+++ b/rest_framework/authentication.py
@@ -204,6 +204,9 @@ def authenticate(self, request):
         except oauth.Error as err:
             raise exceptions.AuthenticationFailed(err.message)
 
+        if not oauth_request:
+            return None
+
         oauth_params = oauth_provider.consts.OAUTH_PARAMETERS_NAMES
 
         found = any(param for param in oauth_params if param in oauth_request)
diff --git a/rest_framework/fields.py b/rest_framework/fields.py
index 4b6931ad46..f3496b53e6 100644
--- a/rest_framework/fields.py
+++ b/rest_framework/fields.py
@@ -494,7 +494,7 @@ class DateField(WritableField):
     }
     empty = None
     input_formats = api_settings.DATE_INPUT_FORMATS
-    format = api_settings.DATE_FORMAT
+    format = None
 
     def __init__(self, input_formats=None, format=None, *args, **kwargs):
         self.input_formats = input_formats if input_formats is not None else self.input_formats
@@ -536,8 +536,8 @@ def from_native(self, value):
         raise ValidationError(msg)
 
     def to_native(self, value):
-        if value is None:
-            return None
+        if value is None or self.format is None:
+            return value
 
         if isinstance(value, datetime.datetime):
             value = value.date()
@@ -557,7 +557,7 @@ class DateTimeField(WritableField):
     }
     empty = None
     input_formats = api_settings.DATETIME_INPUT_FORMATS
-    format = api_settings.DATETIME_FORMAT
+    format = None
 
     def __init__(self, input_formats=None, format=None, *args, **kwargs):
         self.input_formats = input_formats if input_formats is not None else self.input_formats
@@ -605,11 +605,14 @@ def from_native(self, value):
         raise ValidationError(msg)
 
     def to_native(self, value):
-        if value is None:
-            return None
+        if value is None or self.format is None:
+            return value
 
         if self.format.lower() == ISO_8601:
-            return value.isoformat()
+            ret = value.isoformat()
+            if ret.endswith('+00:00'):
+                ret = ret[:-6] + 'Z'
+            return ret
         return value.strftime(self.format)
 
 
@@ -623,7 +626,7 @@ class TimeField(WritableField):
     }
     empty = None
     input_formats = api_settings.TIME_INPUT_FORMATS
-    format = api_settings.TIME_FORMAT
+    format = None
 
     def __init__(self, input_formats=None, format=None, *args, **kwargs):
         self.input_formats = input_formats if input_formats is not None else self.input_formats
@@ -658,8 +661,8 @@ def from_native(self, value):
         raise ValidationError(msg)
 
     def to_native(self, value):
-        if value is None:
-            return None
+        if value is None or self.format is None:
+            return value
 
         if isinstance(value, datetime.datetime):
             value = value.time()
diff --git a/rest_framework/serializers.py b/rest_framework/serializers.py
index a81cbc2919..26c34044cf 100644
--- a/rest_framework/serializers.py
+++ b/rest_framework/serializers.py
@@ -129,13 +129,15 @@ class Meta(object):
     _dict_class = SortedDictWithMetadata
 
     def __init__(self, instance=None, data=None, files=None,
-                 context=None, partial=False, many=None, **kwargs):
+                 context=None, partial=False, many=None,
+                 allow_delete=False, **kwargs):
         super(BaseSerializer, self).__init__(**kwargs)
         self.opts = self._options_class(self.Meta)
         self.parent = None
         self.root = None
         self.partial = partial
         self.many = many
+        self.allow_delete = allow_delete
 
         self.context = context or {}
 
@@ -147,6 +149,13 @@ def __init__(self, instance=None, data=None, files=None,
         self._data = None
         self._files = None
         self._errors = None
+        self._deleted = None
+
+        if many and instance is not None and not hasattr(instance, '__iter__'):
+            raise ValueError('instance should be a queryset or other iterable with many=True')
+
+        if allow_delete and not many:
+            raise ValueError('allow_delete should only be used for bulk updates, but you have not set many=True')
 
     #####
     # Methods to determine which fields to use when (de)serializing objects.
@@ -387,6 +396,20 @@ def field_from_native(self, data, files, field_name, into):
                 # Propagate errors up to our parent
                 raise NestedValidationError(serializer.errors)
 
+    def get_identity(self, data):
+        """
+        This hook is required for bulk update.
+        It is used to determine the canonical identity of a given object.
+
+        Note that the data has not been validated at this point, so we need
+        to make sure that we catch any cases of incorrect datatypes being
+        passed to this method.
+        """
+        try:
+            return data.get('id', None)
+        except AttributeError:
+            return None
+
     @property
     def errors(self):
         """
@@ -408,10 +431,33 @@ def errors(self):
             if many:
                 ret = []
                 errors = []
-                for item in data:
-                    ret.append(self.from_native(item, None))
-                    errors.append(self._errors)
-                self._errors = any(errors) and errors or []
+                update = self.object is not None
+
+                if update:
+                    # If this is a bulk update we need to map all the objects
+                    # to a canonical identity so we can determine which
+                    # individual object is being updated for each item in the
+                    # incoming data
+                    objects = self.object
+                    identities = [self.get_identity(self.to_native(obj)) for obj in objects]
+                    identity_to_objects = dict(zip(identities, objects))
+
+                if hasattr(data, '__iter__') and not isinstance(data, (dict, six.text_type)):
+                    for item in data:
+                        if update:
+                            # Determine which object we're updating
+                            identity = self.get_identity(item)
+                            self.object = identity_to_objects.pop(identity, None)
+
+                        ret.append(self.from_native(item, None))
+                        errors.append(self._errors)
+
+                    if update:
+                        self._deleted = identity_to_objects.values()
+
+                    self._errors = any(errors) and errors or []
+                else:
+                    self._errors = {'non_field_errors': ['Expected a list of items']}
             else:
                 ret = self.from_native(data, files)
 
@@ -450,6 +496,9 @@ def data(self):
     def save_object(self, obj, **kwargs):
         obj.save(**kwargs)
 
+    def delete_object(self, obj):
+        obj.delete()
+
     def save(self, **kwargs):
         """
         Save the deserialized object and return it.
@@ -458,6 +507,10 @@ def save(self, **kwargs):
             [self.save_object(item, **kwargs) for item in self.object]
         else:
             self.save_object(self.object, **kwargs)
+
+        if self.allow_delete and self._deleted:
+            [self.delete_object(item) for item in self._deleted]
+
         return self.object
 
 
@@ -765,3 +818,13 @@ def get_related_field(self, model_field, to_many):
             'many': to_many
         }
         return HyperlinkedRelatedField(**kwargs)
+
+    def get_identity(self, data):
+        """
+        This hook is required for bulk update.
+        We need to override the default, to use the url as the identity.
+        """
+        try:
+            return data.get('url', None)
+        except AttributeError:
+            return None
diff --git a/rest_framework/tests/fields.py b/rest_framework/tests/fields.py
index fd6de77972..19c663d820 100644
--- a/rest_framework/tests/fields.py
+++ b/rest_framework/tests/fields.py
@@ -153,12 +153,22 @@ def test_from_native_invalid_format(self):
 
     def test_to_native(self):
         """
-        Make sure to_native() returns isoformat as default.
+        Make sure to_native() returns datetime as default.
         """
         f = serializers.DateField()
 
         result_1 = f.to_native(datetime.date(1984, 7, 31))
 
+        self.assertEqual(datetime.date(1984, 7, 31), result_1)
+
+    def test_to_native_iso(self):
+        """
+        Make sure to_native() with 'iso-8601' returns iso formated date.
+        """
+        f = serializers.DateField(format='iso-8601')
+
+        result_1 = f.to_native(datetime.date(1984, 7, 31))
+
         self.assertEqual('1984-07-31', result_1)
 
     def test_to_native_custom_format(self):
@@ -289,6 +299,22 @@ def test_to_native(self):
         result_3 = f.to_native(datetime.datetime(1984, 7, 31, 4, 31, 59))
         result_4 = f.to_native(datetime.datetime(1984, 7, 31, 4, 31, 59, 200))
 
+        self.assertEqual(datetime.datetime(1984, 7, 31), result_1)
+        self.assertEqual(datetime.datetime(1984, 7, 31, 4, 31), result_2)
+        self.assertEqual(datetime.datetime(1984, 7, 31, 4, 31, 59), result_3)
+        self.assertEqual(datetime.datetime(1984, 7, 31, 4, 31, 59, 200), result_4)
+
+    def test_to_native_iso(self):
+        """
+        Make sure to_native() with format=iso-8601 returns iso formatted datetime.
+        """
+        f = serializers.DateTimeField(format='iso-8601')
+
+        result_1 = f.to_native(datetime.datetime(1984, 7, 31))
+        result_2 = f.to_native(datetime.datetime(1984, 7, 31, 4, 31))
+        result_3 = f.to_native(datetime.datetime(1984, 7, 31, 4, 31, 59))
+        result_4 = f.to_native(datetime.datetime(1984, 7, 31, 4, 31, 59, 200))
+
         self.assertEqual('1984-07-31T00:00:00', result_1)
         self.assertEqual('1984-07-31T04:31:00', result_2)
         self.assertEqual('1984-07-31T04:31:59', result_3)
@@ -419,13 +445,26 @@ def test_from_native_invalid_format(self):
 
     def test_to_native(self):
         """
-        Make sure to_native() returns isoformat as default.
+        Make sure to_native() returns time object as default.
         """
         f = serializers.TimeField()
         result_1 = f.to_native(datetime.time(4, 31))
         result_2 = f.to_native(datetime.time(4, 31, 59))
         result_3 = f.to_native(datetime.time(4, 31, 59, 200))
 
+        self.assertEqual(datetime.time(4, 31), result_1)
+        self.assertEqual(datetime.time(4, 31, 59), result_2)
+        self.assertEqual(datetime.time(4, 31, 59, 200), result_3)
+
+    def test_to_native_iso(self):
+        """
+        Make sure to_native() with format='iso-8601' returns iso formatted time.
+        """
+        f = serializers.TimeField(format='iso-8601')
+        result_1 = f.to_native(datetime.time(4, 31))
+        result_2 = f.to_native(datetime.time(4, 31, 59))
+        result_3 = f.to_native(datetime.time(4, 31, 59, 200))
+
         self.assertEqual('04:31:00', result_1)
         self.assertEqual('04:31:59', result_2)
         self.assertEqual('04:31:59.000200', result_3)
diff --git a/rest_framework/tests/filterset.py b/rest_framework/tests/filterset.py
index fe92e0bcfa..238da56e5b 100644
--- a/rest_framework/tests/filterset.py
+++ b/rest_framework/tests/filterset.py
@@ -65,7 +65,7 @@ def setUp(self):
 
         self.objects = FilterableItem.objects
         self.data = [
-            {'id': obj.id, 'text': obj.text, 'decimal': obj.decimal, 'date': obj.date.isoformat()}
+            {'id': obj.id, 'text': obj.text, 'decimal': obj.decimal, 'date': obj.date}
             for obj in self.objects.all()
         ]
 
@@ -95,7 +95,7 @@ def test_get_filtered_fields_root_view(self):
         request = factory.get('/?date=%s' % search_date)  # search_date str: '2012-09-22'
         response = view(request).render()
         self.assertEqual(response.status_code, status.HTTP_200_OK)
-        expected_data = [f for f in self.data if datetime.datetime.strptime(f['date'], '%Y-%m-%d').date() == search_date]
+        expected_data = [f for f in self.data if f['date'] == search_date]
         self.assertEqual(response.data, expected_data)
 
     @unittest.skipUnless(django_filters, 'django-filters not installed')
@@ -125,7 +125,7 @@ def test_get_filtered_class_root_view(self):
         request = factory.get('/?date=%s' % search_date)  # search_date str: '2012-10-02'
         response = view(request).render()
         self.assertEqual(response.status_code, status.HTTP_200_OK)
-        expected_data = [f for f in self.data if datetime.datetime.strptime(f['date'], '%Y-%m-%d').date() > search_date]
+        expected_data = [f for f in self.data if f['date'] > search_date]
         self.assertEqual(response.data, expected_data)
 
         # Tests that the text filter set with 'icontains' in the filter class works.
@@ -142,8 +142,7 @@ def test_get_filtered_class_root_view(self):
         request = factory.get('/?decimal=%s&date=%s' % (search_decimal, search_date))
         response = view(request).render()
         self.assertEqual(response.status_code, status.HTTP_200_OK)
-        expected_data = [f for f in self.data if
-                         datetime.datetime.strptime(f['date'], '%Y-%m-%d').date() > search_date and
+        expected_data = [f for f in self.data if f['date'] > search_date and
                          f['decimal'] < search_decimal]
         self.assertEqual(response.data, expected_data)
 
diff --git a/rest_framework/tests/pagination.py b/rest_framework/tests/pagination.py
index 1a2d68a685..d2c9b05137 100644
--- a/rest_framework/tests/pagination.py
+++ b/rest_framework/tests/pagination.py
@@ -102,7 +102,7 @@ def setUp(self):
 
         self.objects = FilterableItem.objects
         self.data = [
-            {'id': obj.id, 'text': obj.text, 'decimal': obj.decimal, 'date': obj.date.isoformat()}
+            {'id': obj.id, 'text': obj.text, 'decimal': obj.decimal, 'date': obj.date}
             for obj in self.objects.all()
         ]
 
diff --git a/rest_framework/tests/serializer.py b/rest_framework/tests/serializer.py
index beb372c2b4..05217f35a0 100644
--- a/rest_framework/tests/serializer.py
+++ b/rest_framework/tests/serializer.py
@@ -112,7 +112,7 @@ def setUp(self):
         self.expected = {
             'email': 'tom@example.com',
             'content': 'Happy new year!',
-            'created': '2012-01-01T00:00:00',
+            'created': datetime.datetime(2012, 1, 1),
             'sub_comment': 'And Merry Christmas!'
         }
         self.person_data = {'name': 'dwight', 'age': 35}
@@ -261,34 +261,6 @@ def test_missing_bool_with_default(self):
         self.assertEqual(serializer.is_valid(), True)
         self.assertEqual(serializer.errors, {})
 
-    def test_bad_type_data_is_false(self):
-        """
-        Data of the wrong type is not valid.
-        """
-        data = ['i am', 'a', 'list']
-        serializer = CommentSerializer(self.comment, data=data, many=True)
-        self.assertEqual(serializer.is_valid(), False)
-        self.assertTrue(isinstance(serializer.errors, list))
-
-        self.assertEqual(
-            serializer.errors,
-            [
-                {'non_field_errors': ['Invalid data']},
-                {'non_field_errors': ['Invalid data']},
-                {'non_field_errors': ['Invalid data']}
-            ]
-        )
-
-        data = 'and i am a string'
-        serializer = CommentSerializer(self.comment, data=data)
-        self.assertEqual(serializer.is_valid(), False)
-        self.assertEqual(serializer.errors, {'non_field_errors': ['Invalid data']})
-
-        data = 42
-        serializer = CommentSerializer(self.comment, data=data)
-        self.assertEqual(serializer.is_valid(), False)
-        self.assertEqual(serializer.errors, {'non_field_errors': ['Invalid data']})
-
     def test_cross_field_validation(self):
 
         class CommentSerializerWithCrossFieldValidator(CommentSerializer):
diff --git a/rest_framework/tests/serializer_bulk_update.py b/rest_framework/tests/serializer_bulk_update.py
index 3ecb23eddc..afc1a1a9fd 100644
--- a/rest_framework/tests/serializer_bulk_update.py
+++ b/rest_framework/tests/serializer_bulk_update.py
@@ -7,6 +7,9 @@
 
 
 class BulkCreateSerializerTests(TestCase):
+    """
+    Creating multiple instances using serializers.
+    """
 
     def setUp(self):
         class BookSerializer(serializers.Serializer):
@@ -71,3 +74,181 @@ def test_bulk_create_errors(self):
         self.assertEqual(serializer.is_valid(), False)
         self.assertEqual(serializer.errors, expected_errors)
 
+    def test_invalid_list_datatype(self):
+        """
+        Data containing list of incorrect data type should return errors.
+        """
+        data = ['foo', 'bar', 'baz']
+        serializer = self.BookSerializer(data=data, many=True)
+        self.assertEqual(serializer.is_valid(), False)
+
+        expected_errors = [
+                {'non_field_errors': ['Invalid data']},
+                {'non_field_errors': ['Invalid data']},
+                {'non_field_errors': ['Invalid data']}
+        ]
+
+        self.assertEqual(serializer.errors, expected_errors)
+
+    def test_invalid_single_datatype(self):
+        """
+        Data containing a single incorrect data type should return errors.
+        """
+        data = 123
+        serializer = self.BookSerializer(data=data, many=True)
+        self.assertEqual(serializer.is_valid(), False)
+
+        expected_errors = {'non_field_errors': ['Expected a list of items']}
+
+        self.assertEqual(serializer.errors, expected_errors)
+
+    def test_invalid_single_object(self):
+        """
+        Data containing only a single object, instead of a list of objects
+        should return errors.
+        """
+        data = {
+            'id': 0,
+            'title': 'The electric kool-aid acid test',
+            'author': 'Tom Wolfe'
+        }
+        serializer = self.BookSerializer(data=data, many=True)
+        self.assertEqual(serializer.is_valid(), False)
+
+        expected_errors = {'non_field_errors': ['Expected a list of items']}
+
+        self.assertEqual(serializer.errors, expected_errors)
+
+
+class BulkUpdateSerializerTests(TestCase):
+    """
+    Updating multiple instances using serializers.
+    """
+
+    def setUp(self):
+        class Book(object):
+            """
+            A data type that can be persisted to a mock storage backend
+            with `.save()` and `.delete()`.
+            """
+            object_map = {}
+
+            def __init__(self, id, title, author):
+                self.id = id
+                self.title = title
+                self.author = author
+
+            def save(self):
+                Book.object_map[self.id] = self
+
+            def delete(self):
+                del Book.object_map[self.id]
+
+        class BookSerializer(serializers.Serializer):
+            id = serializers.IntegerField()
+            title = serializers.CharField(max_length=100)
+            author = serializers.CharField(max_length=100)
+
+            def restore_object(self, attrs, instance=None):
+                if instance:
+                    instance.id = attrs['id']
+                    instance.title = attrs['title']
+                    instance.author = attrs['author']
+                    return instance
+                return Book(**attrs)
+
+        self.Book = Book
+        self.BookSerializer = BookSerializer
+
+        data = [
+            {
+                'id': 0,
+                'title': 'The electric kool-aid acid test',
+                'author': 'Tom Wolfe'
+            }, {
+                'id': 1,
+                'title': 'If this is a man',
+                'author': 'Primo Levi'
+            }, {
+                'id': 2,
+                'title': 'The wind-up bird chronicle',
+                'author': 'Haruki Murakami'
+            }
+        ]
+
+        for item in data:
+            book = Book(item['id'], item['title'], item['author'])
+            book.save()
+
+    def books(self):
+        """
+        Return all the objects in the mock storage backend.
+        """
+        return self.Book.object_map.values()
+
+    def test_bulk_update_success(self):
+        """
+        Correct bulk update serialization should return the input data.
+        """
+        data = [
+            {
+                'id': 0,
+                'title': 'The electric kool-aid acid test',
+                'author': 'Tom Wolfe'
+            }, {
+                'id': 2,
+                'title': 'Kafka on the shore',
+                'author': 'Haruki Murakami'
+            }
+        ]
+        serializer = self.BookSerializer(self.books(), data=data, many=True, allow_delete=True)
+        self.assertEqual(serializer.is_valid(), True)
+        self.assertEqual(serializer.data, data)
+        serializer.save()
+        new_data = self.BookSerializer(self.books(), many=True).data
+        self.assertEqual(data, new_data)
+
+    def test_bulk_update_and_create(self):
+        """
+        Bulk update serialization may also include created items.
+        """
+        data = [
+            {
+                'id': 0,
+                'title': 'The electric kool-aid acid test',
+                'author': 'Tom Wolfe'
+            }, {
+                'id': 3,
+                'title': 'Kafka on the shore',
+                'author': 'Haruki Murakami'
+            }
+        ]
+        serializer = self.BookSerializer(self.books(), data=data, many=True, allow_delete=True)
+        self.assertEqual(serializer.is_valid(), True)
+        self.assertEqual(serializer.data, data)
+        serializer.save()
+        new_data = self.BookSerializer(self.books(), many=True).data
+        self.assertEqual(data, new_data)
+
+    def test_bulk_update_error(self):
+        """
+        Incorrect bulk update serialization should return error data.
+        """
+        data = [
+            {
+                'id': 0,
+                'title': 'The electric kool-aid acid test',
+                'author': 'Tom Wolfe'
+            }, {
+                'id': 'foo',
+                'title': 'Kafka on the shore',
+                'author': 'Haruki Murakami'
+            }
+        ]
+        expected_errors = [
+            {},
+            {'id': ['Enter a whole number.']}
+        ]
+        serializer = self.BookSerializer(self.books(), data=data, many=True, allow_delete=True)
+        self.assertEqual(serializer.is_valid(), False)
+        self.assertEqual(serializer.errors, expected_errors)