Probleme
Call to undefined method Mage_Core_Model_Locale::getDateFormatWithLongYear() in /home/…/public_html/…/app/code/core/Mage/Adminhtml/Block/Widget/Form.php on line 207
Solutions
I fixed by copying
/app/code/core/Mage/Adminhtml/Block/Widget/Form.php to /app/code/local/Mage/Adminhtml/Block/Widget/Form.php
Changing line 207 to read:
$element->setFormat(Mage::app()->getLocale()->getDateFormat(Mage_Core_Model_Locale::FORMAT_TYPE_SHORT));