It is supposed to happen within 3 or 4 days, but I never did get over cravings on Atkins (I gave up after 12 days of induction). I got control of cravings with another low/controlled carb plan (Carbohydrate Addicts Lifespan Program). Everyone is different and people find success with different plans.
What I found later and have also found helpful is Julie Ross's recommendations in The Diet Cure.