Perhaps I am mistaken, but I don't think it is required your CDT be in-character. If you're a creative story writer, it can be fun. If not, noting milestones in your character's life in an OOC list is fine too.
The CDT is for you to revisit over time, to help you stay focused on your PC's personality, goals, difficulties, etc. It is also used as a reference for the GM team should they ever interact with this PC (via CDQ, WLDQ, PRC request).
My opinion, of course.