The book I'm writing at present begins in 1950, when the POV characters are eighteen, six and eight.
I've now worked my way forward to 1962. Like Counterpoint, this story will be a two-parter, because otherwise it will be too long. Many of the events in The Pixie Grip, which is this first part, were pre-determined, because the main characters have appeared before, as secondary characters, in other books in the series. Tracing them through their reported and recorded actions is fun, and it's particularly satisfying to fill in gaps and flesh out some small happenings. For example, Peter P and his wife Pia have four children quite widely spaced. This spacing was the result of something I did in the fourth book of the series, when I unwisely gave Peck, Peter and Pia's grandson, a much older cousin named Ryl. Peck was twenty-eight and Ryl was in her mid-forties. To make that work, I had to account for Peck's mother and Ryl's mother, who were sisters, having children so far apart. Thus the spacing of Peter and Pia's family. Ryl's mother Melody was born in 1951 and Peck's mother Leilana came along in 1967 as the first and last children with two brothers in between.
All that was internal consistency, but setting this story so far back meant researching all manner of things. I was certainly around in 1962, but I don't really remember it.
A selection of things I've had to research includes: 1950s cars, mediaeval folk songs, early 1960s hairstyles and clothing, the date of construction of some Sydney landmarks, the requirements for gaining a drivers' licence in the 1950s, and drinking age. Things I was fairly sure of included pre-decimal currency (which I remember), imperial measurements (ditto), common foods of the time and the prevalence of televisions. Things I was less certain of, and still am, are when certain slang terms and common terms and phrases became common. If I remember my parents saying something when I was very young, then I can assume it was current. If in doubt, I left it out.
I nearly made one error when a character was hitchhiking to a music festival and was picked up by a panel van containing three hippies. I had a sudden doubt and checked. Sure enough, the hippie culture rose in the mid 1960s... It's at least four years too early for Joe to meet his hippies, so I gave him a ride in a family sedan instead. Not as colourful...but more accurate!