Question: Violated Angels is a film based on a mass murder spree which took place when?

Context paragraphs:
Yema stabbings: Yang Qingpei (born 1989 ) is a Chinese man accused of the mass murder of 19 people.  He confessed to killing his parents in an argument over money and then killing 17 neighbours in an attempt to cover up his crime on September 29, 2016, state media reported.  The youngest victim of the murderous rampage in a remote village in southwest China was three, the oldest 72.  They were members of six families.  Suspect Yang Qingpei, aged 28, went to his home village of Yema on Wednesday.  He was arrested in Kunming, capital of Yunnan Province, on Thursday.  The Xinhua state news agency report did not say how the villagers were killed.  Mass killings are rare in China and access to firearms is tightly controlled.  The crime took place in Qujing, Yunnan Province.

Lennoxville massacre: The Lennoxville massacre, or Lennoxville purge, was a mass murder which took place at the Hells Angels clubhouse in Lennoxville, Quebec on March 24, 1985.  Five members of the Hells Angels North Chapter, founded by Laurent "L'Anglais" Viau and Yves "Apache" Trudeau, were shot dead.  This event divided rival outlaw motorcycle gangs in Quebec, leading to the formation of the Rock Machine club, a rival to the Hells in the 1990s.

Siculicidium: The Massacre at Madéfalva took place at Siculeni in Romania.  In Latin "Siculicidium" "murder of Székelys" was a mass murder committed against Székelys by the Habsburg army in 1764, under Maria Theresa.

Badlands (film): Badlands is a 1973 American crime film written and directed by Terrence Malick, starring Martin Sheen and Sissy Spacek, and featuring Warren Oates and Ramon Bieri.  The story, though fictional, is loosely based on the real-life murder spree of Charles Starkweather and his girlfriend, Caril Ann Fugate, in 1958, though that basis was not acknowledged when the film was released.

Hashimpura massacre: The Hashimpura massacre is an alleged incident of mass murder which took place on or around 22 May 1987 near Meerut in Uttar Pradesh state, India, during the 1987 Meerut communal riots.  it is alleged that 19 personnel of the Provincial Armed Constabulary rounded up 42 Muslim youths from the Hashimpura "mohalla" (locality) of the city, took them to the outskirts of the city, shot them in cold blood and dumped their bodies in a nearby irrigation canal.  A few days later, the dead bodies were found floating in the canal and a case of murder was registered.  Eventually, 19 men were accused of having performed the act.  In May 2000, 16 of the 19 accused surrendered and were later released on bail, the other three accused having died in the intervening period.  In 2002, the Supreme Court of India ordered that the case trial be transferred from the Ghaziabad district court to a Sessions Court at the Tis Hazari complex in Delhi.

Valley of Death (Bydgoszcz): Valley of Death (Polish: "Dolina Śmierci" ) in Fordon, Bydgoszcz, northern Poland, is a site of Nazi German mass murder committed at the beginning of World War II; and a mass grave of 1,200 – 1,400 Poles and Jews murdered in October and November 1939 by the local German "Selbstschutz" and the Gestapo.  The murders were a part of Intelligenzaktion in Pomerania, a Nazi action aimed at the elimination of the Polish intelligentsia in Reichsgau Danzig-West Prussia, which included the former Pomeranian Voivodeship ("Polish Corridor").  It was part of a larger genocidal action that took place in all German occupied Poland, code-named Operation Tannenberg.

Silent Night, Deadly Night (franchise): Silent Night, Deadly Night is an American horror franchise consisting of six feature films, action figures, clothing, stockings, Christmas ornaments, and other memorabilia.  The first film in the series, "Silent Night, Deadly Night" (1984), originally titled "Slay Ride", tells the story of Billy, a young man who experiences a psychotic break and goes on a murder spree dressed as Santa Claus.  The film received theatrical distribution from TriStar Pictures, but was pulled from theaters in November 1984 after a series of protests against the film.

Violated Angels: Violated Angels (犯された白衣, , Okasareta Hakui ) is a film made by controversial Japanese director Kōji Wakamatsu in 1967.  Wakamatsu's most famous film, it is based on the mass murder spree of Richard Speck in 1966.

Murder in the Heartland: Murder in the Heartland is a television miniseries that aired on ABC in 1993.  It was based on the 1957–58 murder spree carried out by 19-year-old Charles Starkweather throughout Nebraska and Wyoming.  The first half of the miniseries covers the murders.  The second half covers the trials of Starkweather and Caril Ann Fugate, his 14-year-old girlfriend accomplice.  Their increasingly disparate versions of events are contrasted as the trials unfold.

Richard Speck: Richard Benjamin Speck (December 6, 1941 – December 5, 1991) was an American mass murderer who systematically tortured, raped, and murdered eight student nurses from South Chicago Community Hospital on the night of July 13-14, 1966.

Supporting paragraphs: Violated Angels Richard Speck
Answer: night of July 13-14, 1966