Julie and Porter’s ages when she was pregnant

Does anyone know the age gap between Julie and Porter Scavo? I’m rewatching the series for the first time since I watched it back when it was on air and timelines/ages are so vague! I feel like I’m loving the show more this time around but it is driving me crazy trying to figure out how much time passes between major events.

Julie was a teenager when the show started and the twins were little kids. Then she moves off for college but secretly dropped out when she visits later on. Then when she shows up and is pregnant, she is suddenly in her last year of getting a PhD. When did she go back to college and get to that stage of her education? Do they even try to have ages make sense?