It is usual to plan the dates for a bop at least a week before 0th week of the term. Try to get the dates of big bops at other grad colleges so you don't get a clash (e.g. HalloQueen, Australia Day at St Anthony's). It is also a good idea to schedule bops the same day as university wide events such as the last day of Summer VIIIs. In addition, we have found that having bops after formal halls isn't very good, as you can't reasonably charge entry and it means you are limiting the number of Entz you can do in a term.