Taking from SeX home page.

Attention SceneXpress members,SeX staff has decided to hold open sign-ups the first three days of each month, starting from this December, for a brief duration. We hope to introduce new members into our ranks and bring some renewed energy to the site. Our main reason for opening sign-ups is to ensure a healthy growth, and for that we need more members.
So spread the word - tell your friend's, your family, torrent enthusiasts, and other people you know.

In short: For a brief duration, there will be open sign-ups at the first three days of each month. This means that sign-ups will be open on December 1st, 2nd and 3rd, January 1st, 2nd, 3rd, and February 1st, 2nd, and 3rd, and so on, until staff decides to end it.