Feds and the rates

I keep seeing in the news on a regular basis "feds raised rates" or "feds leave rates alone". I mean that's great. But at first I thought it was like a once per year thing. I guess I never really payed attention. But now I'm thinking that maybe it's once per quarter that they can choose to change rates. Or maybe once per month. Or maybe once per week. I mean it just seems like something that would be more stable since it's something that so much rides on. If feds raise the rates, the stock market crumbles. If they leave the rates the same, stock market does very well. I think they have a vote on it once per month. I mean does the entire global economy change that quick? I say change it when it needs to be changed to stimulate something. Otherwise, let it be and just make an announcment when it changes. Don't tell me every couple of weeks "This just in...nothing new".