[Gretl-users] VAR impulse responses: period 1

Dear Gretl-users, I have a question about the impulse responses of a vector autoregression model, generated with Gretl: The impulse responses start at period 1. Is period 1 the period AFTER the shock or is it the same period of the shock (the contemporaneous period of the shock)? This is perhaps a rather obvious question, but I would like to be sure as I'm analyzing impulse responses for my dissertation. I'm looking forward to your answer! Thanks in advance, Lien