Thank you for this. I looked all over Magento’s horrible forums and couldn’t find any mention of this. There were other references to this error related to mismatched local settings, but that wasn’t my case.

../magento/app/code/core/Mage/Core/Model/Locale.php lines 379 to 381. Change the following:

$convert = array(’yyyy-MM-ddTHH:mm:ssZZZZ’=>’%c’, ‘EEEE’=>’%A’, ‘EEE’=>’%a’,'D’=>’%j’,
‘MMMM’=>’%B’, ‘MMM’=>’%b’, ‘MM’=>’%m’, ‘M’=>’%m’, ‘dd’=>’%d’,
‘d’=>’%e’, ‘yyyy’=>’%Y’, ‘yy’=>’%y’);

to the folowing code:

$convert = array(’yyyy-MM-ddTHH:mm:ssZZZZ’=>’%c’, ‘EEEE’=>’%A’, ‘EEE’=>’%a’,'D’=>’%j’,
‘MMMM’=>’%B’, ‘MMM’=>’%b’, ‘MM’=>’%m’, ‘M’=>’%m’, ‘dd’=>’%d’,
‘d’=>’%d’, ‘yyyy’=>’%Y’, ‘yy’=>’%y’);

Note the ‘d’=>’%d’ in the third line of code makes all the difference. Now, all your dates will work properly now.