Dating conventions

Fans have created a timeline of the Harry Potter series from one shred of information in Harry Potter and the Chamber of Secrets. At Nearly Headless Nick's deathday party in that book, his death is stated to have been on October 31, 1492. Since the celebration was commemorating the five-hundredth anniversary of Nick's death, this seems to say the scene takes place on October 31, 1992. This timeline is reinforced in Harry Potter and the Deathly Hallows when the graves of James and Lily Potter confirm that they were born in 1960 and died on 31 October 1981.

For the sake of convenience, this dating system will be used by the Harry Potter Wiki for all Harry Potter articles.

Dates

 * Events prior to 1800
 * 19th century
 * 20th century
 * 1900s
 * 1910s
 * 1920s
 * 1930s
 * 1940s
 * 1950s
 * 1960s
 * 1970s
 * 1970
 * 1971
 * 1972
 * 1973
 * 1974
 * 1975
 * 1976
 * 1977
 * 1978
 * 1979
 * 1980s
 * 1980
 * 1981
 * 1982
 * 1983
 * 1984
 * 1985
 * 1986
 * 1987
 * 1988
 * 1989
 * 1990s
 * 1990
 * 1991
 * 1992
 * 1993
 * 1994
 * 1995
 * 1996
 * 1997
 * 1998
 * Between 1998 and 2017
 * 21st century
 * 2017
 * After 2017

Contradictions
There are numerous contradictions in the timeline, though it should be noted that Rowling herself has admitted having difficulty with managing mathematics in the FAQ section of her website, so perhaps perfect internal consistency is not to be expected. In addition, considering the Harry Potter universe is a fantasy world, it's possible that certain dates may differ between it and the "real world".

Despite its problems, this timeline is extensively used by fans and Warner Bros.'s timeline of the series (featured on the DVDs for Harry Potter and the Chamber of Secrets and Harry Potter and the Prisoner of Azkaban) contains dates that were interpolated from this dating system (such as Harry's birthday being on July 31 1980 and his first defeat of Lord Voldemort being on October 31 1981.) However, several anachronisms have crept through in the movies, such as featuring the destruction of the Millennium Bridge in the film version of Harry Potter and the Half-Blood Prince, even though the novel (and the film) are supposed to take place a couple of years before the bridge was built. In Harry Potter and the Order of the Phoenix, the Dursleys are seen to have a flat-screen TV, which were not commonly available in the mid-1990s.

A short film with the movie series cast, The Queen's Handbag was produced in 2006 as part of the 80th birthday celebrations for Queen Elizabeth II. The skit violates the dating convention by having the characters reference the event, even though for them it should still be the mid-1990s.

Problems with time
Often when dates are given, they are given with a day of the week that does not match with the said date as it in actual history. Just one such example occurs in Harry Potter and the Prisoner of Azkaban when Sybill Trelawney refers to 16 October as Friday, despite 16 October 1993 being a Saturday. This is usually explained on the grounds of it being simply poetic licence on the author's part.

There are also contradictions within the books themselves in this area. For example, in Harry Potter and the Goblet of Fire, both 1 September and 2 September are given as Mondays and, in Harry Potter and the Prisoner of Azkaban, Buckbeak's trial is set on 20 April, but careful parsing of the text reveals that it could have happened no later than February.

Historical problems
Although the series, according to the timeline derived from the Chamber of Secrets reference, is set in the nineties, the book often seems as though it is set more in the present time. In Harry Potter and the Half-Blood Prince, Cornelius Fudge uses a male pronoun to refer to the "predecessor" of the Prime Minister of the United Kingdom. According to the above timeline, this should occur in the summer of 1996, when the Prime Minister was John Major, whose immediate predecessor was a woman (Margaret Thatcher).

It is possible, however unlikely, that Fudge could be referring to a more distant predecessor, as Thatcher took office before Fudge supposedly became Minister for Magic. (Although one could imagine a scenario in which Fudge was delegated by the Minister for Magic to meet with the Prime Minister while he, Fudge, was in an inferior office.) Additionally, the personality and history of the Prime Minister portrayed appears to more closely match that of Tony Blair than of John Major. An article in the Daily Mail notes that Rowling is close to the Chancellor of the Exchequer Gordon Brown (often viewed as a rival to Blair's leadership of the Labour Party), and that she might have been attempting to show Blair's worst side. If the books were set in sync with publication date of Philosopher's Stone, then this event would occur in 2002 (after Blair became Prime Minister).

A similar problem involves Nicolas Flamel. Flamel was mentioned as being 665 at the time of the first book, but Nicolas Flamel was a real historical figure and would not have reached that age until 1996, around the time the first book was published. The rebuttal for this is that the date the "real" Nicolas Flamel was born does not correspond with the Nicolas Flamel of Harry Potter.

Another problem exists regarding Rubeus Hagrid's tenure as Hogwarts' gamekeeper. It is implied throughout the series that Hagrid was given that position within a few years of his expulsion from school in 1942. But in one scene of Harry Potter and the Goblet of Fire, Molly Weasley reminisces about Ogg, Hagrid's predecessor; since Hagrid's years as gamekeeper appear to overlap with Molly's years at school, it seems unlikely that she remembers a previous gamekeeper. However, it's possible that Hagrid did not become a gamekeeper immediately after being expelled, but rather started out as Ogg's assistant. This is plausible given that when Harry thinks he will be expelled for flying on the broomstick without permission in his first year, he wonders if he would be allowed to stay on as Hagrid's assistant.

There is at least one anachronism in the books. In a letter Harry writes to Sirius in Harry Potter and the Goblet of Fire, he mentions that his cousin Dudley owns a PlayStation. According to the timeline, this would be in the summer of 1994, but that gaming console was not launched anywhere until December of 1994, and even then only in Japan. However, considering his parents gave him whatever he wanted, they could have gone out of Britain to get it, as well as utilize special connections.

Another mistake occurs in dealing with the attendance of Bellatrix Lestrange and Severus Snape at Hogwarts. Sirius Black makes mention of Snape and Bellatrix's attendance of the school overlapping at a certain point; however, this is impossible, as Bellatrix attended the school from either 1962 to 1969 or 1963 to 1970, while Snape started at Hogwarts in 1971. Sirius could have meant that Snape and Bellatrix ran with the same kind of crowd, rather than actual crowd.