I approach writing a period piece as I would approach all my other projects, focusing on the truth of the characters' journeys but primarily it is a fictional world. The past is another country. I write as an intrigued foreigner inspired by a new landscape."The truth of the characters' journey". Lord, give me strength. In plain English, that means that she's a lazy writer who can't be bothered to do her homework and ends up with a load of 21st century characters in fancy dress. That's why they go around spouting tosh like "Note to self" and use "reference" as a verb.
Moral? When doing a period story (or any writing at all) , research, research, research.