Muggles' Guide to Harry Potter/Timeline
Note on dates
Harry Potter and the Chamber of Secrets gives us one concrete date: Sir Nicholas de Mimsy-Porpington (aka Nearly Headless Nick) celebrates the 500th anniversary of his deathday, which occurred 31 October 1492. Working from this, we can date nearly every event mentioned in the books.
The author has evidently decided to adhere to this timeline. In Harry Potter and the Deathly Hallows, we see the gravestone of Harry's parents, and learn, as we had already surmised, that they died on 31 October 1981. We also learn that they were born in 1960.
The author has said that Sirius was about 22 when he went to Azkaban, which was mere days after Harry's parents were killed. From this, we can determine that Harry's parents, who were in the same year as Sirius, would have been born around 1959, which is of course consistent with our assumptions above.
There is one leap of faith: In Harry Potter and the Chamber of Secrets, The Very Secret Diary is mentioned as being "fifty years old", as is Tom Riddle's citation for "services to the school". While it is likely that Lucius Malfoy would have thought it a rare joke to send Riddle's diary to Hogwarts on its fiftieth anniversary, it is possible that "fifty years" in this case means "about fifty years". However, in order to clarify sequence, we have assumed that "fifty years" means exactly that. All dates based on that, however, have an uncertainty of about five years either way – this includes all dates for things occurring in the early life of Tom Riddle.
At least one fan site has placed the death of Tom Riddle's father in 1942, and Moaning Myrtle's death as occurring much later than this, about 1945. Evidence in the books only somewhat supports this theory; Harry Potter and the Chamber of Secrets does state that Myrtle's death occurred in the latter half of Tom Riddle's fifth year at Hogwarts, which would have been the spring of 1943, give or take about five years, and Harry says in Harry Potter and the Half-Blood Prince that Tom Riddle visited the Riddle Manor and killed his father, then returned to the school and asked Professor Slughorn about Horcruxes. When he talked to Slughorn, he was a prefect, so that must have been his fifth or sixth year; not his seventh year, because he was then Head Boy. Harry Potter and the Goblet of Fire does state that Frank Bryce, at the time of his death in what we assume was August 1994, was nearing seventy-seven years old, which places his birth in 1917; it also says he is a veteran of the War, which would have to be the Second World War. Based on this, we have assumed Frank was invalided out of the Army quite early in the War, and tentatively placed the death of the Muggle Tom Riddle in the summer of 1942, followed by the death of Moaning Myrtle in the spring of 1943.
It is interesting to see how many things seem to happen on Hallowe'en. Before the series starts, we have Nearly Headless Nick's death day. Harry's parents are murdered on Hallowe'en, and the troll is let into the school on Hallowe'en in Harry's first year. In Harry's second year, Mrs. Norris is Petrified on Hallowe'en. It is Hallowe'en again when Sirius Black first tries to break into Gryffindor tower in Harry's third year, and when Harry's name comes out of the Goblet of Fire in Harry's fourth year. It is curious, then, that given this long string of Hallowe'en events, that nothing of note seems to happen on Hallowe'en in Harry's fifth, sixth, or seventh years.
Hogwarts, Year One
Hogwarts, Year Two
Hogwarts, Year Three
Events at the Shrieking Shack
Internal evidence suggests that these events, filling more than five of the book's twenty-two chapters, occurred between about 8:30 PM on the last day of exams, and 12:30 AM the following morning, in Harry's third year at Hogwarts. The constraints of the timeline generator require that we assign actual times. We do not intend these times to be taken as in any way being canon, except for 9PM and midnight which are specifically given in the text; all other times are guides only.