They are usually held on Wednesday at 8PM eastern time (this can vary to 7 or 9). The thread is opened and discussions begin. However, the thread remains open during the next days and even months for anyone to post their thought, comments . Many come late to the discussion due to family or a TV conflict. Very informal.
fljoe0 started the group and each week there is a volunteer to pick the next story and be the leader.
You could easily start a thread-- and leave it open for others to respond at a later time that day.