As I ask in the title, what is the right expression, worked days or days worked? Thanks everyone.
Hello Neil, your answer has been perfect to resolve my question. The example is based in the real situation where I found my question. Thanks very much, I can sleep better tonight.
It's impossible to be certain without a context, such as seeing the entire sentence. However, "days worked" is commonly used in the following type of situation: "The workers are paid based on their number of days worked."