Just to clarify

When is our edited version of Posh actually set? I have heard different things, it is essential for me to know the EXACT setting of the piece. As far as i know, the Riot Club go for an extravagant dinner once every term. I also know that their dinner outing in the play is the third from last of the year because of what Toby says to Eddy in the first scene, so according to these indications, I presume that the play is actually set earlier than May.