diff --git a/paramecio2/libraries/db/extrafields/datetimefield.py b/paramecio2/libraries/db/extrafields/datetimefield.py
index 10511d6..c68d028 100644
--- a/paramecio2/libraries/db/extrafields/datetimefield.py
+++ b/paramecio2/libraries/db/extrafields/datetimefield.py
@@ -26,16 +26,17 @@ class DateTimeField(PhangoField):
             value=datetime.local_to_gmt(value)
         
         elif not datetime.obtain_timestamp(value):
-
+            
             self.error=True
             self.txt_error=self.error_default
-            return ''
+            
+            return '0000-00-00 00:00:00'
         
         if value==False:
             
             self.error=True
             self.txt_error=self.error_default
-            return ''
+            return '0000-00-00 00:00:00'
         else:
             
             """
diff --git a/paramecio2/libraries/generate_admin_class.py b/paramecio2/libraries/generate_admin_class.py
index 23101d7..3497132 100644
--- a/paramecio2/libraries/generate_admin_class.py
+++ b/paramecio2/libraries/generate_admin_class.py
@@ -72,6 +72,8 @@ class GenerateAdminClass:
 
         self.url_redirect=self.url
         
+        self.pre_update=None
+        
         self.post_update=None
 
         self.text_home=I18n.lang('common', 'home', 'Home')
@@ -131,6 +133,13 @@ class GenerateAdminClass:
             
             insert_row=self.model.insert
             
+            pre_update_ret=False
+            
+            if not self.pre_update:
+                pre_update_ret=True
+            else:
+                pre_update_ret=self.pre_update(self)
+            
             try:
                 
                 item_id=str(int(request.args.get('id', '0')))
@@ -149,21 +158,36 @@ class GenerateAdminClass:
             
             post=dict(request.form)
             
-            if insert_row(post):
-                flash(I18n.lang('common', 'task_successful', 'Task successful'))
-                
-                if self.post_update:
-                    if item_id=='0':
-                        item_id=self.model.insert_id()
-                    self.post_update(self, item_id)                
-                
-                return redirect(self.url_redirect)
+            if pre_update_ret:
+            
+                if insert_row(post):
+                    flash(I18n.lang('common', 'task_successful', 'Task successful'))
+                    
+                    if self.post_update:
+                        if item_id=='0':
+                            item_id=self.model.insert_id()
+                        self.post_update(self, item_id)                
+                    
+                    return redirect(self.url_redirect)
+                    
+                else:
+                    
+                    url_action=add_get_parameters(self.url, op_admin=2, id=item_id)
+
+                    post=dict(request.form)
+                    
+                    form=show_form(post, edit_forms, self.t, True)
+                    
+                    return self.t.load_template(self.template_insert, admin=self, title_edit=title_edit, form=form, model=self.model, id=item_id, url_action=url_action, enctype=self.model.enctype)
+
+                    
             else:
                 url_action=add_get_parameters(self.url, op_admin=2, id=item_id)
 
                 post=dict(request.form)
                 
                 form=show_form(post, edit_forms, self.t, True)
+                
                 return self.t.load_template(self.template_insert, admin=self, title_edit=title_edit, form=form, model=self.model, id=item_id, url_action=url_action, enctype=self.model.enctype)
 
             
diff --git a/paramecio2/modules/admin/app.py b/paramecio2/modules/admin/app.py
index acdf460..a4755f2 100644
--- a/paramecio2/modules/admin/app.py
+++ b/paramecio2/modules/admin/app.py
@@ -305,7 +305,9 @@ def signup():
             
             forms['privileges']=2
             
-            user_admin.valid_fields=['username', 'email', 'password', 'privileges']
+            forms['last_login']=now()
+            
+            user_admin.valid_fields=['username', 'email', 'password', 'privileges',  'last_login']
             
             user_admin.create_forms()