other than the fact that this is the third thread asking when the darkness show is going on sale... shows at the 9:30 club are generally announced via the website on thursdays.
you can also get updated show information via the email list, which you can join by emailing
list_serve@930.com.
other options include checking the tickets.com website for tickets. listening to ballards 411 every tuesday at 4:11 on dc101.com to hear 9:30 concert announcements.
as far as the club is concerned a show isn't official until they announce it.