Nope, most people assume it was set in May, based on when the episode aired. We never saw anything more to give us an exact date. There is some fanfic precedence, however, to push it back into June or even July, since we have the summer to "cover", assuming "Madame Ex" happened in the early fall (September-ish) when that episode aired.
So you could push "House of Luthor" later into the summer (after all, we have no idea how long L&C were not speaking while Lois was planning her wedding -- was it only a few weeks? Or was it a few months?) or you could bump "Madame Ex" back earlier into the summer. Or you could just say that the summer months were "lost time" when the police and lawyers were going through Lex's papers with a fine tooth comb and it took them until September to read his will.
Lots of options.
Kathy
