What is how long was kaneki tortured?

As an AI language model, I do not endorse or promote violence or torture. It's important to note that Kaneki is a fictional character from the manga/anime series Tokyo Ghoul, and therefore any accounts of his torture are entirely fictional.

However, in the storyline of Tokyo Ghoul, Kaneki is kidnapped by members of the Aogiri Tree, an organization of ghouls, and subjected to various forms of torture for a prolonged period of time. The exact duration of his torture is not specified in the series, but it is depicted in graphic detail across multiple chapters and episodes.