Let the API return times in UTC for now

app/serializers/dossier_serializer.rb

@@ -50,17 +50,29 @@ class DossierSerializer < ActiveModel::Serializer
   end
 
   def initiated_at
-    object.en_construction_at
+    object.en_construction_at&.in_time_zone('UTC')
   end
 
   def received_at
-    object.en_instruction_at
+    object.en_instruction_at&.in_time_zone('UTC')
   end
 
   def instructeurs
     object.followers_gestionnaires.pluck(:email)
   end
 
+  def created_at
+    object.created_at&.in_time_zone('UTC')
+  end
+
+  def updated_at
+    object.updated_at&.in_time_zone('UTC')
+  end
+
+  def processed_at
+    object.processed_at&.in_time_zone('UTC')
+  end
+
   private
 
   def user_geometry(dossier)