Shortcode for Posts within a certain Date?

Thanks for the question and for the link to your site. I like your taste in music.

The [mla_gallery] shortcode supports the WordPress “Date Query”, which has many features to filter a gallery display by dates. Here are some earlier topics with examples:

Gallery based on Date

Attachment Category RSS Feeds

Show Images of a Specic Upload Date

I hope that gets you started on a solution for your application. I am marking this topic resolved, but please update it if you have problems or further questions regarding how to filter your gallery by dates. Thanks for your interest in the plugin.