Question: When was the arena which hosted the Call of Duty: Experience 2016 opened ?

Context articles: Call of Duty: Experience 2011
Call of Duty: Experience 2016
Call of Duty World League
ACHES
Epsilon eSports
Call of Duty (video game)
Call of Duty: Infinite Warfare
100 Thieves
Scump
The Forum (Inglewood, California)

Call of Duty: XP 2011 was the first annual convention hosted by Activision to celebrate their video game series "Call of Duty".
 The convention was held in Los Angeles, California from September 2–3, 2011 in and around a 12-acre hangar where developer Infinity Ward (coupled with Sledgehammer Games) showcased their upcoming game, "" and online service "".
 The convention offered fans an opportunity to observe and participate in various events and attractions such as a $1 million tournament, live performances from various artists, "Call of Duty: Modern Warfare 3" multiplayer, paintball, jeep off-roading, zip-lining, and a full-scale replica of Burger Town from "".
Call of Duty: Experience 2016 (shortened to Call of Duty: XP 2016 and CoD: XP 2016) was the second "Call of Duty" gaming convention held by Activision and Infinity Ward.
 It took place at The Forum in Inglewood, California from September 2 to September 4, 2016.
 Serving as the follow-up to the , the event featured the multiplayer reveal for the upcoming title "" as well as the 2016 Call of Duty World League Championship.
The Call of Duty World League is a "Call of Duty" eSports league that began in January 2016.
 It is played on "" for PlayStation 4 and acts as a qualifier for the pre-existing, annual Call of Duty Championship.
 There are two divisions of play, a Professional division and an Amateur division, with the top teams of both qualifying for the championships.
 A total of $3 million USD of prize money will be given out throughout the year, with the annual Call of Duty Championships handing out $1.6 million.
 The 2016 Winner was Rayan Mendelsohn from Cloud9 (eSports) The league was originally slated to begin on January 5 but was delayed a week for "issues beyond our control", some of which may have stemmed from the previous night's PlayStation Network outage.
 The COD World League officially kicked off on January 13.
Patrick Price, (born July 18, 1994) better known by his gamertag ACHES, is an American professional "Call of Duty" player who was most recently the captain and playing the slayer role for Cloud9; He previously played on 100Thieves the team that was founded by Matt "NaDeSHoT" Haag.
 He won the Call of Duty Championship 2014 with compLexity Gaming.
 He has also played on and is known for teams such as Leverage, compLexity, Evil Geniuses, FaZe Clan, and Cloud9.
 As of September 2016, ACHES has won $273,306, of which nearly half was won in "".
Epsilon eSports is an esports organization that has teams competing in "", Gears "Call of Duty", "FIFA", and "H1Z1" KoH.
 Leading organisation in Console eSports, with multiple championship Call of Duty European Titles over the years 2011-2014.
 Epsilon's Smite team won the Smite World Championship 2016.
 The organization is headquartered in Brussels, Belgium but individual teams are based across Europe and North America.
Call of Duty is a 2003 first-person shooter video game developed by Infinity Ward and published by Activision.
 It is the first of many installments in the "Call of Duty" franchise.
 The game simulates infantry and combined arms warfare of World War II using a modified version of the id Tech 3 engine built for "Quake III: Team Arena".
 Much of its theme and gameplay is similar to the "Medal of Honor" series; however, "Call of Duty" showcases multiple viewpoints staged in the British, American, and Soviet theaters of World War II.
Call of Duty: Infinite Warfare is a first-person shooter video game developed by Infinity Ward and published by Activision.
 It is the thirteenth primary installment in the "Call of Duty" series and was released worldwide for Microsoft Windows, PlayStation 4, and Xbox One on November 4, 2016.
100 Thieves, also known as Hundred Thieves, is a professional American eSports team, founded by Matthew "Nadeshot" Haag on April 18, 2016.
 Upon establishment, 100 Thieves signed the "Call of Duty" team KingPapey in the middle of the Call of Duty World League Relegation Season 1, after they eliminated Call of Duty veterans; Team Kaliber.
 The team currently only competes in Call of Duty.
 The team captain is Patrick "ACHES" Price.
 On May 18, 2016 Nelson left 100 Thieves, calling out the team's lackluster performance.
 However, he rejoined the team on May 23, 2016 after the team released Johnny and Examples, bringing on Remy to the roster.
 The entire roster was released on July 7, 2016 after a last place finish in the Call of Duty World League Season 2.
Seth Abner (born June 30, 1995), known by his handle Scump, is a professional American "Call of Duty" player.
 He is currently the captain of OpTic Gaming since replacing his former team-mate position, Matthew "Nadeshot" Haag, playing the slayer role.
 Abner is a two time Major League Gaming (MLG) X Games gold medalist.
 In August 2017, Seth achieved his first ever Call of Duty World Championship.
 Abner is sponsored by several gaming hardware companies, including Turtle Beach and Scuf Gaming.
 He is also sponsored by Loot Crate, Gymshark, and Brisk Mate.
 On March 26, 2015, Abner became sponsored by Red Bull due to OpTic Gaming's partnership with the company (although he was not a Red Bull eSports athlete), but the partnership ended January 20, 2016.
 As of September 2016, Scump has won $523,543, of which $261,250 was won in "".
 He also runs a very active YouTube channel with over 2.2 million subscribers and over 400 hours of content.
The Forum is a multi-purpose indoor arena in Inglewood, California, adjacent to Los Angeles.
 Located between West Manchester Boulevard, across Pincay Drive and Kareem Court, it is north of the under-construction Los Angeles Stadium at Hollywood Park and the new Hollywood Park Casino.
 It is about three miles east of Los Angeles International Airport.
 Opening on December 30, 1967, the Forum was an unusual and groundbreaking structure.
 Architect Charles Luckman's vision was brought to life by engineers Carl Johnson and Svend Nielsen, who were able to engineer the structure so that it had no major support pillars.
 This had previously been unheard of in an indoor arena the size of the Forum.