diff --git a/app/models/champ.rb b/app/models/champ.rb
index 58ad82378..e509751c7 100644
--- a/app/models/champ.rb
+++ b/app/models/champ.rb
@@ -6,6 +6,9 @@ class Champ < ActiveRecord::Base
   delegate :libelle, :type_champ, :order_place, :mandatory, :description, :drop_down_list, to: :type_de_champ
 
   before_save :format_date_to_iso, if: Proc.new { type_champ == 'date' }
+  before_save :serialize_datetime_if_needed, if: Proc.new { type_champ == 'datetime' }
+  before_save :multiple_select_to_string, if: Proc.new { type_champ == 'multiple_drop_down_list' }
+
   after_save :internal_notification, if: Proc.new { !dossier.nil? }
 
   def mandatory?
@@ -65,9 +68,35 @@ class Champ < ActiveRecord::Base
     self.value = date
   end
 
+  def serialize_datetime_if_needed
+    if (value =~ /=>/).present?
+      date = begin
+      hash_date = YAML.safe_load(value.gsub('=>', ': '))
+      year, month, day, hour, minute = hash_date.values_at(1,2,3,4,5)
+      DateTime.new(year, month, day, hour, minute).strftime("%d/%m/%Y %H:%M")
+      rescue
+        nil
+      end
+
+      self.value = date
+    end
+  end
+
   def internal_notification
     unless dossier.state == 'draft'
       NotificationService.new('champs', self.dossier.id, self.libelle).notify
     end
   end
+
+  def multiple_select_to_string
+    if value.present?
+      json = JSON.parse(value)
+      if json == ['']
+        self.value = nil
+      else
+        json = json - ['']
+        self.value = json.to_s
+      end
+    end
+  end
 end
diff --git a/spec/models/champ_spec.rb b/spec/models/champ_spec.rb
index 868001afc..4769a6e7f 100644
--- a/spec/models/champ_spec.rb
+++ b/spec/models/champ_spec.rb
@@ -4,4 +4,63 @@ describe Champ do
   require 'models/champ_shared_example.rb'
 
   it_should_behave_like "champ_spec"
+
+  describe '#serialize_datetime_if_needed' do
+    let(:type_de_champ) { TypeDeChamp.new(type_champ: 'datetime') }
+    let(:champ) { Champ.new(type_de_champ: type_de_champ, value: value) }
+
+    before { champ.save }
+
+    # when using the old form, and the ChampsService Class
+    # TODO: to remove
+    context 'when the value is already serialized' do
+      let(:value) { '12/01/2017 10:23' }
+
+      it { expect(champ.value).to eq(value) }
+    end
+
+    context 'when the value is not already serialized' do
+      let(:value) { '{ 1=>2017, 2=>01, 3=>12, 4=>10, 5=>23  }' }
+
+      it { expect(champ.value).to eq('12/01/2017 10:23') }
+    end
+  end
+
+  describe '#multiple_select_to_string' do
+    let(:type_de_champ) { TypeDeChamp.new(type_champ: 'multiple_drop_down_list') }
+    let(:champ) { Champ.new(type_de_champ: type_de_champ, value: value) }
+
+    before { champ.save }
+
+    # when using the old form, and the ChampsService Class
+    # TODO: to remove
+    context 'when the value is already deserialized' do
+      let(:value) { '["1", "2"]' }
+
+      it { expect(champ.value).to eq(value) }
+
+      context 'when the value is nil' do
+        let(:value) { nil }
+
+        it { expect(champ.value).to eq(value) }
+      end
+    end
+
+    # for explanation for the "" entry, see
+    # https://apidock.com/rails/ActionView/Helpers/FormOptionsHelper/select
+    # GOTCHA
+    context 'when the value is not already deserialized' do
+      context 'when a choice is selected' do
+        let(:value) { '["", "1", "2"]' }
+
+        it { expect(champ.value).to eq('["1", "2"]') }
+      end
+
+      context 'when all choices are removed' do
+        let(:value) { '[""]' }
+
+        it { expect(champ.value).to eq(nil) }
+      end
+    end
+  end
 end