diff --git a/addons/calendar/calendar.py b/addons/calendar/calendar.py
index 9b251ee80fd..62f149e161d 100644
--- a/addons/calendar/calendar.py
+++ b/addons/calendar/calendar.py
@@ -957,9 +957,7 @@ class calendar_event(osv.Model):
 
     def _check_closing_date(self, cr, uid, ids, context=None):
         for event in self.browse(cr, uid, ids, context=context):
-            if event.start_datetime and event.stop_datetime < event.start_datetime:
-                return False
-            if event.start_date and event.stop_date < event.start_date:
+            if event.stop < event.start:
                 return False
         return True
 
@@ -1007,6 +1005,16 @@ class calendar_event(osv.Model):
 
         return {'value': value}
 
+    def onchange_duration(self, cr, uid, ids, start=False, duration=False, context=None):
+        value = {}
+        if not (start and duration):
+            return value
+        start = datetime.strptime(start, DEFAULT_SERVER_DATETIME_FORMAT)
+        value['stop_date'] = (start + timedelta(hours=duration)).strftime(DEFAULT_SERVER_DATE_FORMAT)
+        value['stop_datetime'] = (start + timedelta(hours=duration)).strftime(DEFAULT_SERVER_DATETIME_FORMAT)
+        value['start_date'] = start.strftime(DEFAULT_SERVER_DATE_FORMAT)
+        return {'value': value}
+
     def onchange_dates(self, cr, uid, ids, fromtype, start=False, end=False, checkallday=False, allday=False, context=None):
 
         """Returns duration and end date based on values passed
@@ -1749,8 +1757,11 @@ class mail_message(osv.Model):
         convert the search on real ids in the case it was asked on virtual ids, then call super()
         '''
         for index in range(len(args)):
-            if args[index][0] == "res_id" and isinstance(args[index][2], basestring):
-                args[index][2] = get_real_ids(args[index][2])
+            if args[index][0] == "res_id":
+                if isinstance(args[index][2], basestring):
+                    args[index][2] = get_real_ids(args[index][2])
+                elif isinstance(args[index][2], list):
+                    args[index] = (args[index][0], args[index][1], map(lambda x: get_real_ids(x), args[index][2]))
         return super(mail_message, self).search(cr, uid, args, offset=offset, limit=limit, order=order, context=context, count=count)
 
     def _find_allowed_model_wise(self, cr, uid, doc_model, doc_dict, context=None):
diff --git a/addons/calendar/calendar_view.xml b/addons/calendar/calendar_view.xml
index 4d17f5c04cc..b90a0b70d83 100644
--- a/addons/calendar/calendar_view.xml
+++ b/addons/calendar/calendar_view.xml
@@ -105,13 +105,14 @@
                                     <field name="start_date" string="Starting at" on_change="onchange_dates('start', start_date, stop_date, allday, True)" attrs="{'invisible': [('allday','=',False)]}"/>
                                     <field name="stop_date" string="Ending at" on_change="onchange_dates('stop', start_date, stop_date, allday, True)" attrs="{'invisible': [('allday','=',False)]}"/>
 
-                                    <field name="start_datetime" string="Starting at" on_change="onchange_dates('start', start_datetime, stop_datetime, allday, False)" attrs="{'invisible': [('allday','=',True)]}"/>
-                                    <field name="stop_datetime" string="Ending at" on_change="onchange_dates('stop', start_datetime, stop_datetime, allday, False)" attrs="{'invisible': [('allday','=',True)]}"/>
-                                    <label for="allday"/>
-                                    <div>
-                                        <field name="allday"  class="oe_inline" on_change="onchange_allday(start, stop, start_date, stop_date, start_datetime, stop_datetime, allday)"/>
+                                    <field name="start_datetime" string="Starting at" on_change="onchange_duration(start_datetime, duration)" attrs="{'invisible': [('allday','=',True)]}"/>
+                                    <field name="stop_datetime" invisible="1"/>
+                                    <label for="duration" attrs="{'invisible': [('allday','=',True)]}"/>
+                                    <div attrs="{'invisible': [('allday','=',True)]}">
+                                        <field name="duration" widget="float_time" string="Duration" on_change="onchange_duration(start_datetime, duration)" class="oe_inline"/>
+                                        <span>hours</span>
                                     </div>
-                                    <field name="duration" widget="float_time" class="oe_inline" attrs="{ 'invisible': True }"/>
+                                    <field name="allday"  on_change="onchange_allday(start, stop, start_date, stop_date, start_datetime, stop_datetime, allday)"/>
                                 </group>
                                 <group>
                                     <field name="categ_ids" widget="many2many_tags" />