The date of Pamela Voorhees' murders in 1979

Question

In the 1980 movie, Friday the 13th, Pamela Voorhees started a killing spree on June 13, 1979. But this date was in fact, a wednesday.

It was July 13th of that year that was a friday.

Was it a mistake or a deliberate error?

Answer 1

The exact year is not really and clearly mentioned. No timeline for this series will ever be perfect, as there are many contradictions present in the films and the spin-off media. Some say the original film was most likely set on Friday, July 13, 1979, some say in 1980, both because of the calendar days. The film takes place on July 4, 1958 and June 13, in "the present day", but at no point in the film do they mention the year.

Screenrant says, in its timeline explained:

After the opening credits of Friday the 13th, a graphic reads: Friday, June 13: The Present. One would assume that the present would mean the year the film was released: 1980. Since June of that year did, indeed, have an actual Friday that fell on the 13th, it’s a safe assumption that the original film takes place on this specific date. While the true age of Jason when he drowned is unknown, Mrs. Voorhees states that “today is his birthday”. This gives some weight to her choosing this particular date for revenge, though later films would not place much significance on an actual date. After the original film, the Friday the 13th date in the titles became more of a symbolic reference.

From a Friday the 13th fandom.

Wednesday, June 13: Pamela Voorhees goes on a killing spree at Camp Crystal Lake, trying to stop the camp from being reopened.

The dates in the movie are from the year 1980 when the movie was released, not 1979 when the movie takes place. June 13, 1979 was a Wednesday and June 14, 1979 was a Thursday. In 1979, the months with the 13th on a Friday were April and July. The two most likely explanations are that either the original film actually takes place in April or July instead of June, or the franchise takes place in a universe where the calendar is slightly different from ours. However, since the dates in most of the other films match our calendar, it is more likely that the events of the first film take place in July (it wouldn’t be April because the school year hadn‘t ended yet so summer camp wouldn’t have started yet). It should be noted that Steve Christy notes the moon is full and in fact in April 13 date is the day after the full moon. April makes sense as well because the victims were preparing the camp to open for the summer.

Additional note: Friday the 13th is considered an unlucky day in Western superstition ¹. And Sean Cunningham wanted Friday the 13th to be shocking, visually stunning, and "[make] you jump out of your seat". He wanted Friday the 13th to be more of a "roller coaster ride". The first film was meant to be "a real scary movie". The concept for Friday the 13th began as nothing more than a title. "A Long Night at Camp Blood" was the working title Victor Miller used while he drafted a script, but Cunningham believed in his "Friday the 13th" moniker ².

To me, it's nothing more than "we have a concept" and we'll do everything needed to make it work, even if it means taking a few liberties/shortcuts with reality/timeline and having inaccuracies. Many universes have the same problem. Once successful and rooted in popular culture, it'll only make fans talk about it and it's free advertising.

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^{1. Friday the 13th - the superstition 2. Friday the 13th - the franchise}