I only register the time I finish a drama or the day I've watched a movie since there is personnal note in the drama rating window on my profile.
Like Manga003 I want to remember when I watched a drama. Each week had a special mood, and the drama was part of it. but if I was not feeling fine at that moment, I could have been unfair with my ratings. In a perfect world, I would take time to rewatch things I didn't like to be sure I have not missed something good. In a perfect world, where I've got time... Plus I like to remember in which order I've seen dramas : it could make sens on the ratings too.
@ylisse, thanks for the information, I was also wondering how to find my old posts!