Ill go out on a limb here and say it makes a huge difference. I have watched the lunar phases while hunting and I will say that for the most part the calendars are spot on. Keep in mind that it isn't only the moon that actually affects hunting, it is the sun, the mood, their relation to each other and their proximity to the location. They have to be calculated for each location. Having said that, not only can they tell you which days are better hunting, they can also tell you what time the game will be moving. I don't let the lunar calendars stop me from hunting, but if I am planning ahead, I use the calendars to do it.