I counted backwards once and figured out I was conceived the same month as my parents’ anniversary. I thought I might’ve been the result of their anniversary trip to Jamaica, and for some reason that made me uncomfortable knowing that. A few years later they were talking about the trip and that they didn’t know my mom was pregnant at the time. So thinking more it made sense that I was actually probably from a week or two beforehand, but then that means mom was drinking while pregnant because she didn’t know (although I’m assuming that early doesn’t have much impact).
I haven’t finished the book, but The Wall Street Journal Guide to Information Graphics is also a good read on the subject.