I am trying to sort posts by their custom field value, which is a date in this format:
9 August 2012, 7:18 am
'orderby' => 'meta_value',
'meta_key' => 'wprss_item_date',
'order' => 'DESC'
Do I need to do some conversion before that can work?
Your date should be stored in descending units, like
yyyy-mm-dd hh:mm:ssfor MySQL to be able to sort on the field.See the MySQL docs for Date, Datetime, and Timestamp data types.