Fixed monthly sales reports (date was 1970) (#3126)

Author: sreichel

app/code/core/Mage/Adminhtml/Block/Report/Sales/Grid/Column/Renderer/Date.php

@@ -89,7 +89,7 @@ public function render(Varien_Object $row)
             try {
                 $data = ($this->getColumn()->getGmtoffset())
                     ? Mage::app()->getLocale()->date($data, $dateFormat)->toString($format)
-                    : Mage::getSingleton('core/locale')->date($data, Zend_Date::ISO_8601, null, false)->toString($format);
+                    : Mage::getSingleton('core/locale')->date($data, $dateFormat, null, false)->toString($format);
             } catch (Exception $e) {
                 $data = ($this->getColumn()->getTimezone())
                     ? Mage::app()->getLocale()->date($data, $dateFormat)->toString($format)