diff --git a/addons/crm/crm.py b/addons/crm/crm.py
index a98fcadb959..28b8469580e 100644
--- a/addons/crm/crm.py
+++ b/addons/crm/crm.py
@@ -123,8 +123,9 @@ class crm_case_section(osv.osv):
                           'tooltip': (month_begin + relativedelta.relativedelta(months=-i)).strftime('%B'),
                           } for i in range(self._period_number - 1, -1, -1)]
         group_obj = obj.read_group(cr, uid, domain, read_fields, groupby_field, context=context)
+        pattern = tools.DEFAULT_SERVER_DATE_FORMAT if obj.fields_get(cr, uid, groupby_field)[groupby_field]['type'] == 'date' else tools.DEFAULT_SERVER_DATETIME_FORMAT
         for group in group_obj:
-            group_begin_date = datetime.strptime(group['__domain'][0][2], tools.DEFAULT_SERVER_DATE_FORMAT)
+            group_begin_date = datetime.strptime(group['__domain'][0][2], pattern)
             month_delta = relativedelta.relativedelta(month_begin, group_begin_date)
             section_result[self._period_number - (month_delta.months + 1)] = {'value': group.get(value_field, 0), 'tooltip': group_begin_date.strftime('%B')}
         return section_result