Not being a native English speaker, I still like to read in English from time to time. In my current book was written that someone "... was three days dying." Does this mean that the person died three days ago, or that the person has been suffering from mortal wounds for three days but is still holding on? The previous chapter with this person ended in him being on fire, but there was nothing said about whether he died. The next chapter about this person started with: "The (...) prince was three days dying."
Edit: Thanks for all the help. After this I read further and it became more clear that indeed the Prince was dead after three days of suffering.
To answer some of your questions, it is not translated, as a matter of fact, the writer was born in New Jersey. He is known to write a bit archaic though.
It could indeed well mean the writer wanted to emphasize his suffering since later in the book, someone who was had a long life of seeing people die, described it as one of the worst things he ever saw.
And furthermore, I left out where the prince was from, to prevent spoilers. This could have made it more difficult to google.