The second specific day refers to the day when the goal of writing a book is set. The little girl set a goal and won the affirmation and commitment of others, so it was called a special day.
Third, the first one she refers to is the old librarian who has passed away, and the second one refers to the little girl who made a promise that year.
The fourth librarian gave the little girl a hope. The little girl wrote a book, which she will put on the exhibition platform. The little girl's dream has come true. She finally wrote a book, which can be published, fulfilled a dream of giving a complete book world, and fulfilled her promise to let her book come out for exhibition. She witnessed this dream with the old librarian.