Question: The series in which Dipper Pines was a character in ended on what date?

Context paragraphs:
Weirdmageddon 3: Take Back The Falls: "Weirdmageddon 3: Take Back The Falls" is the series finale of the American animated television series "Gravity Falls", created by Alex Hirsch.  The episode was written by Shion Takeuchi, Mark Rizzo, Josh Weinstein, Jeff Rowe, and Hirsch, and directed by Stephen Sandoval.  The series follows twelve-year-old twins Dipper (voiced by Jason Ritter) and Mabel Pines (voiced by Kristen Schaal), who stay for the summer with their grand uncle Grunkle Stan (voiced by Hirsch) in a tourist trap called the Mystery Shack, set within the fictional town of Gravity Falls, Oregon.  In this episode, Ford (voiced by J.K. Simmons) discovers the extent of Bill Cipher's plans, while the Mystery Shack crew forms a plan to fight back and reclaim the town.  A final confrontation with Bill leads to the Pines family's ultimate fate and greatest sacrifice.

List of Gravity Falls episodes: "Gravity Falls" is an American animated series created by Alex Hirsch for Disney Channel, and now for Disney XD.  The series revolves around the various antics of two fraternal twins, Dipper (voiced by Jason Ritter) and Mabel Pines (voiced by Kristen Schaal), who were handed over to their Great Uncle (or "Grunkle") Stan (voiced by Alex Hirsch), who runs a tourist trap called The Mystery Shack, in the town of Gravity Falls, Oregon.  They soon realize that the mysterious town holds plenty of secrets.  When Dipper obtains an old journal that he finds in the forest, they find that their everyday lifestyle changes with odd things and creatures they encounter.

Jason Ritter: Jason Morgan Ritter (born February 17, 1980) is an American actor, and the son of actress Nancy Morgan and actor John Ritter, known for his roles as Kevin Girardi in the television series "Joan of Arcadia", Ethan Haas in "The Class", as Sean Walker in the NBC series "The Event", and as the voice of Dipper Pines in "Gravity Falls".  He also played the recurring role of Mark Cyr in the NBC television series "Parenthood", for which he received an Emmy Award nomination.

Nancy Drew: Nancy Drew is a fictional American character in a mystery fiction series created by publisher Edward Stratemeyer as the female counterpart to his Hardy Boys series.  The character first appeared in 1930.  The books are ghostwritten by a number of authors and published under the collective pseudonym Carolyn Keene.  Over the decades, the character evolved in response to changes in US culture and tastes.  The books were extensively revised and shortened, beginning in 1959, in part to lower printing costs with arguable success.  In the revision process, the heroine's original character was changed to be less assertive and more feminine.  In the 1980s, an older and more professional Nancy emerged in a new series, "The Nancy Drew Files", that included romantic subplots for the sleuth.  The original "Nancy Drew Mystery Stories" series started in 1930, and ended in 2004.  Launched that same year, the "Girl Detective" series features Nancy driving a hybrid electric vehicle and using a cell phone.  In 2013, the "Girl Detective" series ended, and a new current series called "Nancy Drew Diaries" was launched.  Illustrations of the character evolved over time to reflect contemporary styles.  The character proves continuously popular worldwide: at least 80 million copies of the books have been sold, and the books have been translated into over 45 languages.  Nancy Drew is featured in five films, two television shows, and a number of popular computer games; she also appears in a variety of merchandise sold around the world.

Not What He Seems: "Not What He Seems" is the eleventh episode of the second season of the American animated television series "Gravity Falls", created by Alex Hirsch.  The episode was written by Shion Takeuchi, Josh Weinstein, Jeff Rowe, Matt Chapman, and Hirsch, and directed by Stephen Sandoval.  The series follows twelve-year-old twins Dipper (voiced by Jason Ritter) and Mabel Pines (voiced by Kristen Schaal), who stay for the summer with their grand uncle Grunkle Stan (voiced by Hirsch) in a tourist trap called the Mystery Shack, set within the fictional town of Gravity Falls, Oregon.  In this episode, Dipper and Mabel begin to question who Stan really is after officers arrest him for stealing chemical waste.  The episode, which breaks the show's status quo by revealing Stan's brother, ends with a cliffhanger to the second half of the season.

Dipper Pines: Mason "Dipper" Pines is a fictional character and one of the main characters of the Disney XD animated series "Gravity Falls".  The character is voiced by Jason Ritter, and designed by and loosely based on the childhood of series creator, Alex Hirsch.  The character first appeared on the unreleased, unnamed pilot created by Hirsch with which he pitched the show; he later appeared on the first episode "Tourist Trapped".  Dipper, along with his twin sister Mabel Pines, stars in every episode of the show.  Dipper is the star of the Gravity Falls series of shorts titled "Dipper's Guide to the Unexplained" and also appears in the shorts "Fixin' it with Soos" and "Mabel's Guide to Life".

Mabel Pines: Mabel Pines is one of the lead characters of the Disney XD (formerly Disney Channel) animated series "Gravity Falls".  The character is voiced by Kristen Schaal, and designed by the series creator, Alex Hirsch.  She is inspired by Hirsch's own twin sister, Ariel Hirsch.  Mabel first appeared on the unreleased, unnamed pilot created by Hirsch which he used to pitch the show; she then appeared on the first episode "Tourist Trapped".  Mabel, with her brother Dipper Pines, stars in every episode of the show.  Mabel also has two series of shorts dedicated to her: "Mabel's Guide to Life" and "Mabel's Scrapbook".

Gravity Falls: Gravity Falls is an American animated television series produced by Disney Television Animation originally for Disney Channel (and then later for Disney XD) from June 15, 2012 to February 15, 2016.

Dane DeHaan: Dane William DeHaan ( ; born February 6, 1986) is an American actor.  His roles include Jesse on the HBO series "In Treatment", Andrew Detmer in "Chronicle" (2012), Jason Kancam in Derek Cianfrance's "The Place Beyond the Pines" (2012), Lucien Carr in "Kill Your Darlings" (2013), Harry Osborn in "The Amazing Spider-Man 2" (2014), James Dean in Anton Corbijn's "Life" (2015), Lockhart in Gore Verbinski's "A Cure for Wellness" (2016) and the title character in Luc Besson's "Valerian and the City of a Thousand Planets" (2017).  He has also appeared in several advertisements for Prada.

J. K. Simmons: Jonathan Kimble "J. K." Simmons (born January 9, 1955) is an American character actor and voice actor.  In television, he is known for playing Dr. Emil Skoda on the NBC series "Law & Order" (and other "Law & Order" franchise series), neo-Nazi Vernon Schillinger on the HBO prison-drama "Oz", and Assistant Police Chief Will Pope on TNT's "The Closer".  His film roles include J. Jonah Jameson in Sam Raimi's "Spider-Man" trilogy and music instructor Terence Fletcher in 2014's "Whiplash".  He is also known for voicing Cave Johnson in the video game "Portal 2" (2011), Tenzin in "The Legend of Korra" (2012), Stanford Pines in "Gravity Falls", Kai in "Kung Fu Panda 3" (2016), Mayor Lionheart in "Zootopia" (2016) and Khampa in "Rock Dog" (2016).  Simmons also reprised his role as J. Jonah Jameson in various Marvel animated series and video games.  He has also appeared in a series of highly popular television commercials for Farmers Insurance.

Supporting paragraphs: Dipper Pines Gravity Falls
Answer: February 15, 2016