Ceiling Lights Quit Working?

I have a 3 bedroom house and the ceiling lights in all three rooms and the dining room are no longer working. They worked 4 days ago and now they have stopped. These 4 lights are the only thing on the breaker. I've flipped the breaker a few times and reset all of the GFIs in my house. I have no idea why the lights quit working. I'm slowly updating a 1963 original house and I've replaced 2 of the 4 lights and all the switches associated with them. Does anyone have any suggestions?