diff --git a/dav_events/converters.py b/dav_events/converters.py
index 161392e..682188f 100644
--- a/dav_events/converters.py
+++ b/dav_events/converters.py
@@ -2,92 +2,72 @@ import datetime
 import logging
 import re
 
-from django.http import QueryDict
-
-from . import models
-
 logger = logging.getLogger(__name__)
 
 
-class SessionDict(QueryDict):
-    _re_iso8601 = re.compile(r'^ISO8601:(?P<date>'
-                                r'(?P<year>\d{4})'
-                                r'-(?P<mon>(0[1-9])|(1[012]))'
-                                r'-(?P<day>(0[1-9])|([12][0-9])|(3[01]))'
-                             r')?(?P<sep>.)?'
-                             r'(?P<time>'
-                                r'(?P<hour>([01][0-9])|(2[0123]))'
-                                r':(?P<min>[0-5][0-9])'
-                                r':(?P<sec>[0-5][0-9])'
-                                r'([\,\.]\d{1,10})?'
-                             r')?'
-                             r'(?P<offset>[\-+](([01][0-9])|(2[0123]))(:[0-5][0-9])?)?$')
+class Iso8601Serializer(object):
+    marker = 'ISO8601'
+    separator = ':'
 
-    def __init__(self, instance=None, *args, **kwargs):
-        if 'mutable' in kwargs:
-            raise TypeError('__init__(): got an unexpected keyword argument \'mutable\'')
-        kwargs['mutable'] = True
-        super(SessionDict, self).__init__(*args, **kwargs)
+    _re = re.compile(r'^(?P<date>'
+                     r'(?P<year>\d{4})'
+                     r'-(?P<mon>(0[1-9])|(1[012]))'
+                     r'-(?P<day>(0[1-9])|([12][0-9])|(3[01]))'
+                     r')?(?P<sep>.)?'
+                     r'(?P<time>'
+                     r'(?P<hour>([01][0-9])|(2[0123]))'
+                     r':(?P<min>[0-5][0-9])'
+                     r':(?P<sec>[0-5][0-9])'
+                     r'([,.]\d{1,10})?'
+                     r')?'
+                     r'(?P<offset>[\-+](([01][0-9])|(2[0123]))(:[0-5][0-9])?)?$')
+
+    def __init__(self, instance=None, text=None):
         if instance is not None:
-            self.update(instance)
+            self.instance = instance
+        elif text is not None:
+            self.instance = Iso8601Serializer.deserialize(text)
 
-    def _deserialize_value(self, value):
-        if isinstance(value, basestring):
-            m = self._re_iso8601.match(value)
+    @property
+    def str(self):
+        return Iso8601Serializer.serialize(self.instance)
+
+    @classmethod
+    def serialize(cls, value, ignore_unsupported_input=False):
+        strval = None
+        if isinstance(value, datetime.datetime):
+            strval = value.isoformat()
+        elif isinstance(value, datetime.date):
+            strval = value.isoformat()
+        elif isinstance(value, datetime.time):
+            strval = value.isoformat()
+        elif not ignore_unsupported_input:
+            raise ValueError('Expected datetime.datetime, datetime.date or datetime.time,'
+                             ' not {}'.format(value.__class__.__name__))
+
+        if strval is not None:
+            value = '{marker}{sep}{str}'.format(marker=cls.marker, sep=cls.separator, str=strval)
+
+        return value
+
+    @classmethod
+    def deserialize(cls, value, ignore_unsupported_input=False):
+        prefix = '{marker}{sep}'.format(marker=cls.marker, sep=cls.separator)
+        if isinstance(value, basestring) and value.startswith(prefix):
+            haystack = value[len(prefix):]
+            m = cls._re.match(haystack)
             if m is not None:
-                # logger.debug('SessionDict._deserialize_value(): found iso8601 date \'%s\'', value)
                 gd = m.groupdict()
                 if gd['hour'] is None:
                     value = datetime.date(int(gd['year']), int(gd['mon']), int(gd['day']))
-                    # logger.debug('SessionDict._deserialize_value(): converted into datetime.date \'%s\'', value)
                 elif gd['year'] is None:
                     value = datetime.time(hour=int(gd['hour']), minute=int(gd['min']), second=int(gd['sec']))
-                    # logger.debug('SessionDict._deserialize_value(): converted into datetime.time \'%s\'', value)
                 else:
                     value = datetime.datetime(int(gd['year']), int(gd['mon']), int(gd['day']),
                                               hour=int(gd['hour']), minute=int(gd['min']), second=int(gd['sec']))
-                    # logger.debug('SessionDict._deserialize_value(): converted into datetime.datetime \'%s\'', value)
+            elif not ignore_unsupported_input:
+                raise ValueError('Format not recognized \'{str}\''.format(str=haystack))
+        elif not ignore_unsupported_input:
+            raise ValueError('Expected basestring,'
+                             ' not {}'.format(value.__class__.__name__))
         return value
-
-    def _serialize_value(self, value):
-        if isinstance(value, datetime.datetime):
-            # logger.debug('SessionDict._serialize_value(): found datetime.datetime \'%s\'', value)
-            value = u'ISO8601:{}'.format(value.isoformat())
-            # logger.debug('SessionDict._serialize_value(): converted into unicode \'%s\'', value)
-        elif isinstance(value, datetime.date):
-            # logger.debug('SessionDict._serialize_value(): found datetime.date \'%s\'', value)
-            value = u'ISO8601:{}'.format(value.isoformat())
-            # logger.debug('SessionDict._serialize_value(): converted into unicode \'%s\'', value)
-        elif isinstance(value, datetime.time):
-            # logger.debug('SessionDict._serialize_value(): found datetime.time \'%s\'', value)
-            value = u'ISO8601:{}'.format(value.isoformat())
-            # logger.debug('SessionDict._serialize_value(): converted into unicode \'%s\'', value)
-        return value
-
-    @property
-    def session_data(self):
-        ret = dict()
-        for k in self:
-            ret[k] = self._serialize_value(self[k])
-        return ret
-
-    def update(self, data):
-        for k in data:
-            self[k] = self._deserialize_value(data[k])
-
-
-def event_factory(data):
-    kwargs = dict()
-    if 'deadline' in data:
-        buf = data['deadline']
-        if isinstance(buf, basestring):
-            deadline_choice = buf.lower()
-            deadline_field = 'deadline_{}'.format(deadline_choice)
-            if deadline_field in data:
-                data['deadline'] = data[deadline_field]
-
-    for field in data:
-        if hasattr(models.Event, field):
-            kwargs[field] = data[field]
-
-    return models.Event(**kwargs)
\ No newline at end of file
diff --git a/dav_events/forms.py b/dav_events/forms.py
index d74183e..b0cac6d 100644
--- a/dav_events/forms.py
+++ b/dav_events/forms.py
@@ -5,11 +5,14 @@ import logging
 from babel.dates import format_date
 
 from django import forms
+from django.core.exceptions import ImproperlyConfigured
 from django.utils.translation import get_language, ugettext, ugettext_lazy as _
 from datetimewidget.widgets import DateWidget, TimeWidget, DateTimeWidget
 
 from . import choices
 from . import config
+from . import converters
+from . import models
 
 logger = logging.getLogger(__name__)
 DEVELOPMENT_INIT_FORMS = True
@@ -19,13 +22,30 @@ class ChainedForm(forms.Form):
     _next_form_name = None
 
     def __init__(self, *args, **kwargs):
-        previous_data = kwargs.pop('previous_data', dict())
+        self._session_data = dict()
+        if 'session_data' in kwargs:
+            self.add_session_data(kwargs.pop('session_data'))
         super(ChainedForm, self).__init__(*args, **kwargs)
-        self._proceed_previous_data(previous_data)
+        self._proceed_session_data(self._session_data)
 
-    def _proceed_previous_data(self, previous_data):
+    def _proceed_session_data(self, session_data):
         pass
 
+    def _serialize_value(self, value):
+        return converters.Iso8601Serializer.serialize(value, ignore_unsupported_input=True)
+
+    def _deserialize_value(self, value):
+        return converters.Iso8601Serializer.deserialize(value, ignore_unsupported_input=True)
+
+    def _get_model(self):
+        if not hasattr(self, '_model'):
+            raise ImproperlyConfigured('{cls} is missing a Model.'
+                                       ' Define {cls}._model'.format(cls=self.__class__.__name__))
+        return self._model
+
+    def _get_object(self, model_kwargs):
+        return self._get_model()(**model_kwargs)
+
     @property
     def form_name(self):
         return self.__class__.__name__
@@ -51,8 +71,43 @@ class ChainedForm(forms.Form):
     def get_next_form_name(cls):
         return cls._next_form_name
 
+    def get_session_data(self):
+        data = dict()
+        for k in self._session_data:
+            data[k] = self._serialize_value(self._session_data[k])
+        for k in self.cleaned_data:
+            data[k] = self._serialize_value(self.cleaned_data[k])
+        return data
 
-class ModeForm(ChainedForm):
+    def add_session_data(self, data):
+        for k in data:
+            self._session_data[k] = self._deserialize_value(data[k])
+
+    def save(self):
+        object_kwargs = dict()
+        data = self._session_data
+        data.update(self.cleaned_data)
+        if 'deadline' in data:
+            buf = data['deadline']
+            if isinstance(buf, basestring):
+                deadline_choice = buf.lower()
+                deadline_field = 'deadline_{}'.format(deadline_choice)
+                if deadline_field in data:
+                    data['deadline'] = data[deadline_field]
+
+        model = self._get_model()
+        for field in data:
+            if hasattr(model, field):
+                object_kwargs[field] = data[field]
+
+        return self._get_object(object_kwargs)
+
+
+class EventCreateForm(ChainedForm):
+    _model = models.Event
+
+
+class ModeForm(EventCreateForm):
     _form_title = _(u'Veranstaltungsmodus')
     _next_form_name = 'LocationForm'
 
@@ -151,7 +206,7 @@ class ModeForm(ChainedForm):
         return super(ModeForm, self).next_form_name
 
 
-class TrainingForm(ChainedForm):
+class TrainingForm(EventCreateForm):
     _form_title = _(u'Kursinhalte / Kursziele')
     _next_form_name = 'LocationForm'
 
@@ -163,16 +218,16 @@ class TrainingForm(ChainedForm):
                                      widget=forms.TextInput(attrs={'placeholder': _(u'Kann frei gelassen werden')}))
     course_topic_3 = forms.CharField(required=False,
                                      label=u'%s - %s 3' % (_(u'Kursinhalt'), _(u'Absatz')),
-                                     widget = forms.TextInput(attrs={'placeholder': _(u'Kann frei gelassen werden')}))
+                                     widget=forms.TextInput(attrs={'placeholder': _(u'Kann frei gelassen werden')}))
     course_topic_4 = forms.CharField(required=False,
                                      label=u'%s - %s 4' % (_(u'Kursinhalt'), _(u'Absatz')),
-                                     widget = forms.TextInput(attrs={'placeholder': _(u'Kann frei gelassen werden')}))
+                                     widget=forms.TextInput(attrs={'placeholder': _(u'Kann frei gelassen werden')}))
     course_topic_5 = forms.CharField(required=False,
                                      label=u'%s - %s 5' % (_(u'Kursinhalt'), _(u'Absatz')),
-                                     widget = forms.TextInput(attrs={'placeholder': _(u'Kann frei gelassen werden')}))
+                                     widget=forms.TextInput(attrs={'placeholder': _(u'Kann frei gelassen werden')}))
     course_topic_6 = forms.CharField(required=False,
                                      label=u'%s - %s 6' % (_(u'Kursinhalt'), _(u'Absatz')),
-                                     widget = forms.TextInput(attrs={'placeholder': _(u'Kann frei gelassen werden')}))
+                                     widget=forms.TextInput(attrs={'placeholder': _(u'Kann frei gelassen werden')}))
 
     course_goal_1 = forms.CharField(required=True,
                                     label=u'%s - %s 1' % (_(u'Kursziel'), _(u'Absatz')),
@@ -194,7 +249,7 @@ class TrainingForm(ChainedForm):
                                     widget=forms.TextInput(attrs={'placeholder': _(u'Kann frei gelassen werden')}))
 
 
-class LocationForm(ChainedForm):
+class LocationForm(EventCreateForm):
     _form_title = _(u'Ort')
     _next_form_name = 'ApproachForm'
 
@@ -216,10 +271,10 @@ class LocationForm(ChainedForm):
                                            u' wo das ganze stattfindet.'),
                                widget=forms.TextInput(attrs={'placeholder': u'Karlsruhe'}))
 
-    def _proceed_previous_data(self, previous_data):
-        super(LocationForm, self)._proceed_previous_data(previous_data)
+    def _proceed_session_data(self, session_data):
+        super(LocationForm, self)._proceed_session_data(session_data)
 
-        sport = previous_data.get('sport', None)
+        sport = session_data.get('sport', None)
         if sport == 'B':
             self.fields['terrain'].initial = 'alpine'
             self.fields['location'].widget.attrs['placeholder'] = u'Ramsau, Berchtesgadener Alpen'
@@ -237,7 +292,7 @@ class LocationForm(ChainedForm):
             self.fields['location'].initial = self.fields['location'].widget.attrs['placeholder']
 
 
-class ApproachForm(ChainedForm):
+class ApproachForm(EventCreateForm):
     _form_title = _(u'An- und Abreise / Unterkunft')
     _next_form_name = 'RequirementsForm'
 
@@ -316,13 +371,13 @@ class ApproachForm(ChainedForm):
                                   label=_(u'Andere Verpflegung'),
                                   )
 
-    def _proceed_previous_data(self, previous_data):
-        super(ApproachForm, self)._proceed_previous_data(previous_data)
+    def _proceed_session_data(self, session_data):
+        super(ApproachForm, self)._proceed_session_data(session_data)
 
-        last_day = previous_data.get('last_day', None)
-        sport = previous_data.get('sport', None)
-        country = previous_data.get('country', None)
-        terrain = previous_data.get('terrain', None)
+        last_day = session_data.get('last_day', None)
+        sport = session_data.get('sport', None)
+        country = session_data.get('country', None)
+        terrain = session_data.get('terrain', None)
 
         self.fields['transport_other'].widget.attrs['placeholder'] = _(u'Nebenstehendes Feld beachten')
         self.fields['meeting_point_other'].widget.attrs['placeholder'] = _(u'Nebenstehendes Feld beachten')
@@ -345,7 +400,7 @@ class ApproachForm(ChainedForm):
             self.fields['accommodation_other'].widget = forms.HiddenInput()
 
 
-class RequirementsForm(ChainedForm):
+class RequirementsForm(EventCreateForm):
     _form_title = _(u'Voraussetungen / Vorbedingungen')
     _next_form_name = 'DescriptionForm'
 
@@ -400,12 +455,12 @@ class RequirementsForm(ChainedForm):
                                                               },
                                                               bootstrap_version=3))
 
-    def _proceed_previous_data(self, previous_data):
-        super(RequirementsForm, self)._proceed_previous_data(previous_data)
+    def _proceed_session_data(self, session_data):
+        super(RequirementsForm, self)._proceed_session_data(session_data)
 
-        sport = previous_data.get('sport', None)
-        level = previous_data.get('level', None)
-        terrain = previous_data.get('terrain', None)
+        sport = session_data.get('sport', None)
+        level = session_data.get('level', None)
+        terrain = session_data.get('terrain', None)
 
         if sport == 'B':
             self.fields['equipment'].initial = u'%s (%s)' % (
@@ -465,7 +520,7 @@ class RequirementsForm(ChainedForm):
                 self.fields['requirements'].initial = _(u'Gehzeit X-Y Stunden, ca. X km, ca. X Hm')
 
 
-class DescriptionForm(ChainedForm):
+class DescriptionForm(EventCreateForm):
     _form_title = _(u'Titel / Beschreibung')
     _next_form_name = 'RegistrationForm'
 
@@ -475,14 +530,14 @@ class DescriptionForm(ChainedForm):
     description = forms.CharField(label=_(u'Beschreibung'),
                                   widget=forms.Textarea(attrs={'placeholder': u''}))
 
-    def _proceed_previous_data(self, previous_data):
-        super(DescriptionForm, self)._proceed_previous_data(previous_data)
+    def _proceed_session_data(self, session_data):
+        super(DescriptionForm, self)._proceed_session_data(session_data)
 
-        mode = previous_data.get('mode', None)
-        sport = previous_data.get('sport', None)
-        level = previous_data.get('level', None)
-        terrain = previous_data.get('terrain', None)
-        last_day = previous_data.get('last_day', None)
+        mode = session_data.get('mode', None)
+        sport = session_data.get('sport', None)
+        level = session_data.get('level', None)
+        terrain = session_data.get('terrain', None)
+        last_day = session_data.get('last_day', None)
 
         title_prefix = u''
         if mode == 'training':
@@ -510,7 +565,7 @@ class DescriptionForm(ChainedForm):
         self.fields['title'].initial = title_prefix
 
 
-class RegistrationForm(ChainedForm):
+class RegistrationForm(EventCreateForm):
     _form_title = _(u'Teilnehmer / Anmeldung')
     _next_form_name = 'TrainerForm'
 
@@ -544,10 +599,10 @@ class RegistrationForm(ChainedForm):
                                                            },
                                                        bootstrap_version=3))
 
-    def _proceed_previous_data(self, previous_data):
-        super(RegistrationForm, self)._proceed_previous_data(previous_data)
+    def _proceed_session_data(self, session_data):
+        super(RegistrationForm, self)._proceed_session_data(session_data)
 
-        first_day = previous_data.get('first_day', None)
+        first_day = session_data.get('first_day', None)
         if first_day:
             new_choices = []
             for key, desc in self.fields['deadline'].choices:
@@ -571,7 +626,7 @@ class RegistrationForm(ChainedForm):
             self.fields['deadline'].choices = new_choices
 
 
-class TrainerForm(ChainedForm):
+class TrainerForm(EventCreateForm):
     _form_title = _(u'Tourenleitung')
     _next_form_name = 'ChargesForm'
 
@@ -616,8 +671,8 @@ class TrainerForm(ChainedForm):
                                       help_text=_(u'Kann freigelassen werden'),
                                       )
 
-    def _proceed_previous_data(self, previous_data):
-        super(TrainerForm, self)._proceed_previous_data(previous_data)
+    def _proceed_session_data(self, session_data):
+        super(TrainerForm, self)._proceed_session_data(session_data)
 
         self.fields['trainer_firstname'].widget.attrs['placeholder'] = _(u'Erik')
         self.fields['trainer_familyname'].widget.attrs['placeholder'] = _(u'Müller')
@@ -636,7 +691,7 @@ class TrainerForm(ChainedForm):
             self.fields['trainer_email'].initial = self.fields['trainer_email'].widget.attrs['placeholder']
 
 
-class ChargesForm(ChainedForm):
+class ChargesForm(EventCreateForm):
     _form_title = _(u'Kosten')
     _next_form_name = 'OverviewForm'
 
@@ -669,19 +724,19 @@ class ChargesForm(ChainedForm):
                                        label=_(u'Zusätzliche Kosten (Text)'),
                                        )
 
-    def _proceed_previous_data(self, previous_data):
-        super(ChargesForm, self)._proceed_previous_data(previous_data)
+    def _proceed_session_data(self, session_data):
+        super(ChargesForm, self)._proceed_session_data(session_data)
 
-        mode = previous_data.get('mode', None)
-        sport = previous_data.get('sport', None)
-        ski_lift = previous_data.get('ski_lift', False)
-        terrain = previous_data.get('terrain', None)
-        country = previous_data.get('country', None)
-        first_day = previous_data.get('first_day', None)
-        arrival_previous_day = previous_data.get('arrival_previous_day', False)
-        last_day = previous_data.get('last_day', None)
-        pre_meeting_1 = previous_data.get('pre_meeting_1', None)
-        pre_meeting_2 = previous_data.get('pre_meeting_2', None)
+        mode = session_data.get('mode', None)
+        sport = session_data.get('sport', None)
+        ski_lift = session_data.get('ski_lift', False)
+        terrain = session_data.get('terrain', None)
+        country = session_data.get('country', None)
+        first_day = session_data.get('first_day', None)
+        arrival_previous_day = session_data.get('arrival_previous_day', False)
+        last_day = session_data.get('last_day', None)
+        pre_meeting_1 = session_data.get('pre_meeting_1', None)
+        pre_meeting_2 = session_data.get('pre_meeting_2', None)
 
         if ski_lift:
             charge_key = 'K'
@@ -801,5 +856,5 @@ class ChargesForm(ChainedForm):
         self.fields['additional_costs'].initial = additional_costs_text
 
 
-class OverviewForm(ChainedForm):
+class OverviewForm(EventCreateForm):
     _form_title = _(u'Übersicht')
\ No newline at end of file
diff --git a/dav_events/views.py b/dav_events/views.py
index 43a200c..ed05ea5 100644
--- a/dav_events/views.py
+++ b/dav_events/views.py
@@ -6,7 +6,6 @@ from django.http import HttpResponseRedirect
 from django.urls import reverse_lazy
 from django.views import generic
 
-from . import converters
 from . import forms
 from . import models
 
@@ -64,18 +63,15 @@ class EventCreateView(generic.FormView):
         return context
 
     def form_valid(self, form):
-        previous_data = converters.SessionDict(
-            self.request.session.get('dav_events_event_create_previous_data', dict()))
-        previous_data.update(form.cleaned_data)
-
-        event = converters.event_factory(previous_data)
+        form.add_session_data(self.request.session.get('dav_events_event_create_previous_data', dict()))
+        event = form.save()
 
         next_form_name = form.next_form_name
         if next_form_name:
-            self.request.session['dav_events_event_create_previous_data'] = previous_data.session_data
+            self.request.session['dav_events_event_create_previous_data'] = form.get_session_data()
             self.request.session['dav_events_event_create_next_form_name'] = next_form_name
             next_form_class = self.get_form_class(next_form_name)
-            next_form = next_form_class(previous_data=previous_data)
+            next_form = next_form_class(session_data=form.get_session_data())
             return self.render_to_response(self.get_context_data(form=next_form, event=event))
         else:
             event.save()