diff --git a/addons/caldav/caldav_node.py b/addons/caldav/caldav_node.py
index beff8f56405..16188c4fd84 100644
--- a/addons/caldav/caldav_node.py
+++ b/addons/caldav/caldav_node.py
@@ -28,6 +28,18 @@ import base64
 from document import nodes
 import StringIO
 
+def _str2time(cre):
+    """ Convert a string with time representation (from db) into time (float)
+    """
+    if not cre:
+        return time.time()
+    frac = 0.0
+    if isinstance(cre, basestring) and '.' in cre:
+        fdot = cre.find('.')
+        frac = float(cre[fdot:])
+        cre = cre[:fdot]
+    return time.mktime(time.strptime(cre,'%Y-%m-%d %H:%M:%S')) + frac
+
 class node_database(nodes.node_database):
     def _child_get(self, cr, name=False, parent_id=False, domain=None):
         dirobj = self.context._dirobj
@@ -103,10 +115,7 @@ class node_calendar_collection(nodes.node_dir):
 
     def _get_wtag(self, cr):
         """ Return the modification time as a unique, compact string """
-        if self.write_date:
-            wtime = time.mktime(time.strptime(self.write_date, '%Y-%m-%d %H:%M:%S'))
-        else: wtime = time.time()
-        return str(wtime)
+        return str(_str2time(self.write_date))
 
     def _get_ttag(self, cr):
         return 'calendar collection-%d' % self.dir_id
@@ -277,10 +286,7 @@ class node_calendar(nodes.node_class):
 
     def _get_wtag(self, cr):
         """ Return the modification time as a unique, compact string """
-        if self.write_date:
-            wtime = time.mktime(time.strptime(self.write_date, '%Y-%m-%d %H:%M:%S'))
-        else: wtime = time.time()
-        return str(wtime)
+        return str(_str2time(self.write_date))
 
     def rmcol(self, cr):
         return False
@@ -311,8 +317,9 @@ class res_node_calendar(nodes.node_class):
         self.calendar_id = hasattr(parent, 'calendar_id') and parent.calendar_id or False
         if res_obj:
             if not self.calendar_id: self.calendar_id = res_obj.id
-            self.create_date = res_obj.create_date
-            self.write_date = res_obj.write_date or res_obj.create_date
+            pr = res_obj.perm_read()[0]
+            self.create_date = pr.get('create_date')
+            self.write_date = pr.get('write_date') or pr.get('create_date')
             self.displayname = res_obj.name
 
         self.content_length = 0
@@ -441,9 +448,6 @@ class res_node_calendar(nodes.node_class):
 
     def _get_wtag(self, cr):
         """ Return the modification time as a unique, compact string """
-        if self.write_date:
-            wtime = time.mktime(time.strptime(self.write_date, '%Y-%m-%d %H:%M:%S'))
-        else: wtime = time.time()
-        return str(wtime)
+        return str(_str2time(self.write_date))
 
 # vim:expandtab:smartindent:tabstop=4:softtabstop=4:shiftwidth=4
diff --git a/addons/document_webdav/dav_fs.py b/addons/document_webdav/dav_fs.py
index 248b0e3ce60..b3ab45e2380 100644
--- a/addons/document_webdav/dav_fs.py
+++ b/addons/document_webdav/dav_fs.py
@@ -59,6 +59,19 @@ class DAV_NotFound2(DAV_NotFound):
             args = (path, )
         DAV_NotFound.__init__(self, *args)
 
+
+def _str2time(cre):
+    """ Convert a string with time representation (from db) into time (float)
+    """
+    if not cre:
+        return time.time()
+    frac = 0.0
+    if isinstance(cre, basestring) and '.' in cre:
+        fdot = cre.find('.')
+        frac = float(cre[fdot:])
+        cre = cre[:fdot]
+    return time.mktime(time.strptime(cre,'%Y-%m-%d %H:%M:%S')) + frac
+    
 class openerp_dav_handler(dav_interface):
     """
     This class models a OpenERP interface for the DAV server
@@ -420,18 +433,14 @@ class openerp_dav_handler(dav_interface):
     @memoize(CACHE_SIZE)
     def get_lastmodified(self, uri):
         """ return the last modified date of the object """
-        today = time.time()
         cr, uid, pool, dbname, uri2 = self.get_cr(uri)
         if not dbname:
-            return today
+            return time.time()
         try:            
             node = self.uri2object(cr, uid, pool, uri2)
             if not node:
                 raise DAV_NotFound2(uri2)
-            if node.write_date:
-                return time.mktime(time.strptime(node.write_date,'%Y-%m-%d %H:%M:%S'))
-            else:
-                return today
+            return _str2time(node.write_date)
         finally:
             if cr: cr.close()
 
@@ -456,11 +465,8 @@ class openerp_dav_handler(dav_interface):
             node = self.uri2object(cr, uid, pool, uri2)
             if not node:
                 raise DAV_NotFound2(uri2)
-            if node.create_date:
-                result = time.mktime(time.strptime(node.create_date,'%Y-%m-%d %H:%M:%S'))
-            else:
-                result = time.time()
-            return result
+            
+            return _str2time(node.create_date)
         finally:
             if cr: cr.close()