2000 Year Diary

The Two Thousand Year Diary was a journal kept by the Twelfth Doctor.

It was an updated version of his Twelve Hundred Year Diary (TV: The History of the Doctor, which was, in turn, a continuation of his Nine Hundred Year Diary (TV: Doctor Who), which itself was a follow-up on his Five Hundred Year Diary. (TV: The Power of the Daleks et.al.)

The Doctor used the Two Thousand Year Diary to remind himself of the Mire after they threatened a Viking village. (TV: The Girl Who Died)

At some point the diary would be replaced by the Five Thousand Year Diary. (GAME: Lost in Time)

Behind the scenes
In the second instalment of the parodical comic series The Daft Dimension, the Twelfth Doctor had an incredibly oversized copy of the Two Thousand Year Diary which he struggled to lift. (NOTVALID: The Daft Dimension)