I know I will have more accurate due date once I meet with my doctor.. but my LMP was January 25, telling me my conception date was February 8. I actually know I ovulated on February 10 due to tracking but on my other app (Ovia) if I changed my conception date it changes the date of my LMP and vice Versa. I know it's only a two day difference, but do you calculate based on your conception date if you know it or your LMP?