Diaries & Journals
From Nookipedia, the Animal Crossing wiki
Journals & Diaries only feature in Animal Crossing, as small books that could be written in by the player. There is a page for every month of the year in each diary. Anything can be written within them, but there is limited space. The diary also lists town events. If the player has attended an event, a smile will appear next to its name. Diaries can, if the player wishes, be locked, as other players can view them if they are left out.
Despite looking very different, each diary has the same function and layout. Players start off with the College Rule in their homes when they first start out.
In all later Animal Crossing games, they were replaced by the ability for players to send letters to their future selves.