When does the new Nivida or AMD cards come out?

I am planning a whole new build this summer or coming winter depending on when new parts are being released. I am wondering though, when does Nivida and/or AMD usually announce or release their new GPUs, or do they do it every other year? If you have any ideas when they release new GPUs please let me know. Thanks!

its usually i would say and roughly a year and a few months apart from each other. Right now there is no News on AMD GPUS since they've just released their R7 and R9 Series GPUS a couple of months back. however Nvidia is coming with 800 Series GPU's sometime this summer or this fall with their new Maxwell Architecture.