diff --git a/product/ERP5Form/Form.py b/product/ERP5Form/Form.py
index d949b58d211887bf796bd14e7e1d4757f4f48380..eb1fa238fb520a1ec001ecfc1f5759d279f74872 100644
--- a/product/ERP5Form/Form.py
+++ b/product/ERP5Form/Form.py
@@ -142,12 +142,11 @@ def get_value(self, id, **kw):
         #value=value() # Mising call ??? XXX Make sure compatible with listbox methods
 
     if id == 'default':
-        if self.meta_type != 'DateTimeField':
-          # We make sure we convert values to empty strings
-          # for most fields (so that we do not get a 'value'
-          # message on screeen)
-          # This can be overriden by useing TALES in the field
-          if value is None: value = ''
+        # We make sure we convert values to empty strings
+        # for most fields (so that we do not get a 'value'
+        # message on screen)
+        # This can be overriden by using TALES in the field
+        if value is None: value = ''
 
     return value
 
diff --git a/product/ERP5Form/FormulatorPatch.py b/product/ERP5Form/FormulatorPatch.py
index 884321885c707aad3ab6cba95603054310e50ed3..367c32a6738dbb68eefef813aee26119b2ee04b2 100644
--- a/product/ERP5Form/FormulatorPatch.py
+++ b/product/ERP5Form/FormulatorPatch.py
@@ -806,7 +806,10 @@ class PatchedDateTimeWidget(DateTimeWidget):
             return date_result
     
     def format_value(self, field, value, mode='html'):
-        if value is None:
+        # Is it still usefull to test the None value,
+        # as DateTimeField should be considerer as the other field
+        # and get an empty string as default value?
+        if value in (None, ''):
             return ''
 
         use_ampm = field.get_value('ampm_time_style')
@@ -1121,6 +1124,7 @@ def Field_render_htmlgrid(self, value=None, REQUEST=None, key=None):
   value = self._get_default(widget_key, value, REQUEST)
   __traceback_info__ = ('key=%s value=%r' % (key, value))
   return self.widget.render_htmlgrid(self, widget_key, value, REQUEST)
+
 Field.render_htmlgrid = Field_render_htmlgrid
 
 def Widget_render_htmlgrid(self, field, key, value, REQUEST):