I remember very vividly when I started "Bullet Journaling" (see comment for day 1): i showed up at school a few times that were close together and was surprised when people asked me if i had studied for an exam. I did not, in fact, because i'd clean forgotten that i had any exams at all.

I started keeping a diary in high school after reading The Princess Diaries series. I'm on and off with it. Some of it is on paper and some of it is digital. I've been looking at those 5-year daily journals though, to start on January 1^st.