At Nearly Headless Nick's deathday party in that book, his death is stated to have been on 31 October, 1492.
Since the celebration was commemorating the five-hundredth anniversary of Nick's death, this seems to say the scene takes place on 31 October, 1992. Rowling confirmed, via her Twitter account that that was the day the Epilogue was set.
However, it was later stated that 22 November was a Tuesday, which it was in 1994.
Although the series, according to the timeline derived from the Chamber of Secrets reference, is set in the nineties, the series often seems as though it is set in the late nineties to mid-2000s, roughly concurrent with the publication of the books.
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.
Also, in Harry Potter and the Goblet of Fire it is said that the Champions were chosen on Saturday 31 October, but 31 October was a Monday in 1994.
An article in the Daily Mail notes that Rowling is close to the then-Chancellor of the Exchequer Gordon Brown (often viewed as a rival to Blair's leadership of the Labour Party, who succeeded him and became Prime Minister), and that she might have been attempting to show Blair's worst side.
The actor spent a decade — including the of puberty, umm yikes — in the role over the course of the franchises’ eight films, and in being such an integral part of the series, we’re sure it’s difficult to take himself out of the experience to watch (or even read) the series. I end up having to take a selfie [for a fan] most days, but I’ve never really minded if it makes people happy – though I hate it when people take pictures without asking," Grint told the Radio Times, adding that being in the public eye as a teenager was definitely a bit difficult.
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 31 July 1980 and his first defeat of Lord Voldemort being on 31 October 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 two years before the bridge was built.
In a new interview with the Radio Times, the red-haired actor behind Ron Weasley revealed that starring in the hit film franchise has ultimately “ruined” the series for him as a fan.
sound pretty harsh, but we can definitely understand the sentiment.