Eight and a half years

"'He's changed so much, I barely recognised him.' Severus felt winded by the words and had to steady himself against the wall for a moment, hanging his head in the dark hallway. So that's what she thought of him, now." In which Hermione and Severus had fallen in love in the past, and Severus had given her up. Severus cannot forget, and Hermione cannot forgive.