It’s the fall of the trio’s sixth year, before Hermione’s sixteenth birthday. During a late night conversation with Lavender and Parvati, they ask Hermione whether she’s ever kissed a guy. She replies no. They get into a long discussion about sweet and sour sixteen birthdays, and how it makes you sound so innocent to have a sweet sixteen. The conversation bothers Hermione, and she needs someone to talk to about it. And that someone ends up being Harry.