1967

In the Season 6 episode, Witchstock, Paige, Piper and Phoebe go back in time to the year 1967. Paige goes back at first by wearing a pair of Grams' go-go-boots which Grams had put a return to owner spell on. Piper and Phoebe decided to go back to bring her back to 2004. It was also the year in which Allen Halliwell, the Charmed Ones' grandfather, died.