Belly celebrates her 21st birthday in episode 4 of The Summer I Turned Pretty season 3.
Episode 4 is titled “Last Stand,” and its story includes Belly’s birthday, wedding planning, and pressure surrounding the Cousins Beach house. The birthday establishes that the characters are now in their early twenties rather than the teenagers seen at the beginning of the series.
This fact is easy to mix up with the season finale, which centers on Belly’s 22nd birthday. The two birthdays occur at different points in the season and are separated by the story’s later changes in location and relationships.
Belly is also known by her full name, Isabel Conklin, and is played by Lola Tung. The series uses the nickname “Belly” throughout, so questions about her age and birthday can appear under either name. Her birthday scenes help mark the season’s time jumps and emotional transitions.