Good luck! When I was filling in mine, I started at 2002. I decided that would be the start of the "Frequent Flyer Era" as it's when I started keeping paper records of everything from registration numbers to departure and arrival times. Plus, that was the first year I made sure to earn mileage on every flight I took and the first year I became an elite. Maybe you can find a similar lime of demarcation in your life and add accordingly.