The Five Hundred Year Diary was a journal kept by the Doctor.
According to one account, the First Doctor began writing the diary whilst still on Gallifrey, but left it there when escaping with Susan. It was returned to him by his mentor the Hermit, shortly before the Doctor's regeneration into his second form. (PROSE: The Three Paths)
Another account had the Doctor writing in his Five Hundred Diary from his stay at 76 Totter's Lane onwards. (PROSE: Extracts from the Doctor's 500 Year Diary) He hid the diary in the lower compartment of the astral map. To the Eighth Doctor's surprise, Susan knew the Doctor's hiding place during their original travels. (AUDIO: The Shoreditch Intervention)
While on Earth, the Fourth Doctor checked his pockets for his diary, which contained notes he had made about the Sontarans. (TV: The Sontaran Experiment) When facing the CyberNomads on Nerva Beacon, the Fourth Doctor once again consulted his diary for its records on cybermats and a cyber-virus. (AUDIO: Return of the Cybermen)
The Fourth Doctor searched inside the TARDIS' for the Five Hundred Year Diary, in order to find the DNA code of the Daleks, which he previously recorded. He believed that he left it in the Cloister Room. However, Romana I told him that it was in the swimming pool. Once he located the diary, he programmed the Quantum Gateway to erase the nearby Dalek fleet. (AUDIO: The Final Phase)
By the final time of his fifth incarnation, the Doctor confessed to Peri Brown he tried keeping a diary, not chronological, but "the trouble with time travel is one never seems to find the time". (TV: The Caves of Androzani)
- It is disputable if he was referring to the Five Hundred Year Diary.
By the time he was travelling with Lucie Miller, the Eighth Doctor had the Five Hundred Year Diary in the TARDIS library. He used the book to pinpoint which species of alien was threatening Little Morton. He was able to correctly guess that he was dealing with a Quitoxin. (AUDIO: The Young Lions)
The Eighth Doctor later checked his "secret diary" to confirm his first incarnation's activities on 7 August 1963. He learned that the First Doctor had been relocating the Hand of Omega. (AUDIO: The Shoreditch Intervention)
The Tenth Doctor had a psychic diary written on psychic paper. He explained to Christina that it held everything he saw and felt. The Doctor kept this diary on a desk in the TARDIS's library, but due to a cloud layer in the library's upper stacks, the desk was rained on no matter where it was placed. The Doctor was forced to use a saucepan to catch the rain so it didn't moulder the psychic paper and produce psychic mould and psychic mushrooms. (PROSE: Keeping up with the Joneses)
The Eleventh Doctor had a Twelve Hundred Year Diary, which he and Clara read it when the Doctor forgot everything about himself. His memories were returned after reading the book. (TV: The History of the Doctor)
Scandrius, a Time Lord who idolised the Doctor, carried a Five Hundred Year Diary of his own which he wrote while briefly travelling with Tegan Jovanka in a TARDIS that he stole. (AUDIO: Time in Office)
During one of the times River Song had borrowed the TARDIS, she read the Five Hundred Year Diary. When she found herself in the Great Intelligence's takeover of London, she used her memories of the diary to safely navigate around history. (AUDIO: The Web of Time)
Behind the scenes
References in invalid sources
Information recorded in the Doctor's Five Hundred Year Diary concerning The Doomsday Contract stated that there was once a man, John Lloyd, who worked with Douglas Adams on The Hitchhiker's Guide to the Galaxy. Not long after, Douglas became a script editor on Doctor Who, which prompted Lloyd to submit a story treatment entitled The Doomsday Contract. Lloyd toiled over many redrafts of the script, but it fell through and never made it television.
43 years later, the "remarkable" company Big Finish adapted The Doomsday Weapon into a "full cast audio version". It was a massive success. (NOTVALID: Tom Baker stars in John Lloyd's lost Doctor Who adventure, The Doomsday Contract)