I've been thinking about that...
Harry is 17 throughout most of Book 7. Nineteen years later would make him 36. But wait! The Epilogue takes place in the fall, with students leaving for Hogwarts, which means Harry would have had another birthday, making him 37. Ginny would be a year younger, at 36.
Albus Severus is leaving for his first year at Hogwarts, at age 11. Ginny of course was also 11 years old for her first year, which means that Albus is departing for Hogwarts on the 25th anniversary of his mother's first trip to school.
It's sort of implied in the conversation on the train platform that young James is a year older than Albus, which means his first year at Hogwarts was 25 years after Harry's first year.
If you subtract twelve (James' age) from nineteen you get seven, the number of years between Voldemort's defeat and James' birth. Wondering what Harry & Ginny might have been up to, I did some figuring... allowing one year (roughly) from the wedding to James' birth, we can guess that Harry & Ginny were married no later than six years after Voldy's defeat.
If they both returned to Hogwart's to complete their studies, that's at least one more year, and possibly two if Ginny had to repeat her sixth year. If Harry took Auror training after that, that would have been another three years at least. That leaves a gap of two years between Harry becoming an auror and their wedding.
Here's some intriguing speculation: if Ginny also became an auror, and was still trailing Harry by a year, then we're only left with one year between the end of her training and the wedding.
Given Harry's fame, and the size of the Weasely family, I could imagine an engagement of at least one year for them to plan the wedding. Heck, a two year engagement wouldn't be hard to imagine... well, maybe it would be hard to imagine that either one of them would want to wait that long! But that pretty much accounts for the time between Voldy's end and Harry & Ginny's wedding.
They shoulda eloped...