diff --git a/product/ERP5/tests/testInventoryAPI.py b/product/ERP5/tests/testInventoryAPI.py
index a604a97c6a624bf8a933c2c9363281f3260e5fdd..c81580b61f0f370a794d4d68f1ddbdfc469eb248 100644
--- a/product/ERP5/tests/testInventoryAPI.py
+++ b/product/ERP5/tests/testInventoryAPI.py
@@ -1393,20 +1393,23 @@ class TestNextNegativeInventoryDate(InventoryAPITestCase):
                          start_date=start_date,
                          simulation_state='planned')
     node_uid = self.node.getUid()
-    date = DateTime(DateTime().strftime('%Y/%m/%d'))
+    date = DateTime()
     self.assertEquals(getNextNegativeInventoryDate(node_uid=node_uid), None)
     makeMovement(quantity=1, change_way=1, start_date=date)
     self.assertEquals(getNextNegativeInventoryDate(node_uid=node_uid), None)
     makeMovement(quantity=3, change_way=0, start_date=date+2)
-    self.assertEquals(getNextNegativeInventoryDate(node_uid=node_uid), date+2)
+    self.assertEquals((date + 2).Date(),
+        getNextNegativeInventoryDate(node_uid=node_uid).Date())
     makeMovement(quantity=5, change_way=1, start_date=date+1)
     self.assertEquals(getNextNegativeInventoryDate(node_uid=node_uid), None)
     makeMovement(quantity=7, change_way=0, start_date=date+5)
-    self.assertEquals(getNextNegativeInventoryDate(node_uid=node_uid), date+5)
+    self.assertEquals((date + 5).Date(),
+        getNextNegativeInventoryDate(node_uid=node_uid).Date())
     makeMovement(quantity=7, change_way=1, start_date=date+4)
     self.assertEquals(getNextNegativeInventoryDate(node_uid=node_uid), None)
     makeMovement(quantity=7, change_way=0, start_date=date+3)
-    self.assertEquals(getNextNegativeInventoryDate(node_uid=node_uid), date+3)
+    self.assertEquals((date + 3).Date(),
+                 getNextNegativeInventoryDate(node_uid=node_uid).Date())
 
 class TestInventoryStat(InventoryAPITestCase):
   """Tests Inventory Stat methods.