Ronald,
>>I ask this question because I want to delete more then one
at a time.
You can do this via the databases (ow_blog_post table).
But once you delete blogs there, you will also need to check other tables which are connected to blogs and clean them as well ( for example ow_base_entity_tag, where tags for blogs are saved).
>>
Is there away to delete blog post after they reach a cretin
age like 30 days?
Currently Oxwall doesn't have this feature.
It is a reasonable suggestion though. Can you post is at UserVoice? Thank you.