Lost Years

When Hermione Granger stumbles into a portrait and emerges seven years later, without aging day and having only lost five minutes of her time, Severus Snape is the only one-man welcoming party there to greet her when she emerges. With her friends happily married, and now seven years her senior, it's up to Severus Snape to brew her an aging potion, which is easier said than done.