Some coworkers and I were talking and were trying to figure out if this rumor is true.

If you currently work a 9-5 and your employer decides they want people to work on shifts, is there a 6 month time they have to wait after notifiying you to work shifts?

No, there is no such legal requirement in any state. They could legally change your schedule tomorrow (or even today), if they wanted to.

Boy, someone got that up out of the whole cloth. I can't even think of a law that might be misinterpreted as saying a six month notice was required.