diff --git a/addons/purchase/purchase.py b/addons/purchase/purchase.py
index 1d7745a82f7..581c055db7c 100644
--- a/addons/purchase/purchase.py
+++ b/addons/purchase/purchase.py
@@ -25,7 +25,8 @@ import time
 import netsvc
 
 import ir
-from mx import DateTime
+from datetime import datetime
+from dateutil.relativedelta import relativedelta
 import pooler
 from tools import config
 from tools.translate import _
@@ -518,7 +519,7 @@ class purchase_order_line(osv.osv):
                         'uom': uom,
                         'date': date_order,
                         })[pricelist]
-        dt = (DateTime.now() + DateTime.RelativeDateTime(days=seller_delay or 0.0)).strftime('%Y-%m-%d %H:%M:%S')
+        dt = (datetime.now() + relativedelta(days=seller_delay or 0.0)).strftime('%Y-%m-%d %H:%M:%S')
         prod_name = self.pool.get('product.product').name_get(cr, uid, [prod.id])[0][1]