Question: When did the arena open that hosted UFC 88?

Context paragraphs:
UFC 88: UFC 88: Breakthrough was a mixed martial arts event held by the Ultimate Fighting Championship (UFC) on September 6, 2008 at Philips Arena in Atlanta, Georgia.  The event was headlined by a light heavyweight bout between Chuck Liddell and Rashad Evans.

UFC 138: UFC 138: Leben vs. Muñoz was a mixed martial arts event held by the Ultimate Fighting Championship on November 5, 2011 at LG Arena in Birmingham, United Kingdom.  The event aired on the same day, via tape delay, on Spike TV in the United States and live on Sportsnet in Canada.  The event was the second that the UFC has hosted in Birmingham, the first was UFC 89 back in 2008 also featuring Chris Leben in the main event.

UFC 124: UFC 124: St-Pierre vs. Koscheck 2 was a mixed martial arts pay-per-view event held by the Ultimate Fighting Championship on December 11, 2010 at Bell Centre in Montreal, Quebec, Canada.  The event was the fourth that the UFC has hosted at the Bell Centre following UFC 83, UFC 97 and UFC 113 and the fifth event held in Canada along with UFC 115 which was held in Vancouver, British Columbia.

UFC 121: UFC 121: Lesnar vs. Velasquez was a mixed martial arts event held by the Ultimate Fighting Championship on October 23, 2010 at the Honda Center in Anaheim, California, United States.  The event was the fourth time the UFC has hosted at the Honda Center (formerly Arrowhead Pond) in Anaheim, California following UFC 59, UFC 63 and UFC 76 and the sixth event held in the Greater Los Angeles Area along with UFC 60 and UFC 104.

Philips Arena: Philips Arena is a multi-purpose indoor arena located in Atlanta, Georgia, and is home to the Atlanta Hawks, of the National Basketball Association, and the Atlanta Dream, of the Women's National Basketball Association.  It also served as home to the National Hockey League's Atlanta Thrashers from 1999 to 2011, before the team moved to Winnipeg.  It opened in 1999 at a cost of $213.5 million, replacing the Omni Coliseum.  It is owned by the Atlanta Fulton County Recreation Authority and operated by Tony Ressler, who also, with a group of investors that includes Grant Hill, owns the Hawks.

UFC on Fox: Johnson vs. Benavidez 2: UFC on Fox: Johnson vs. Benavidez 2 (also known as UFC on Fox 9) was a mixed martial arts event held on December 14, 2013, at the Sleep Train Arena in Sacramento, California.  It was the UFC's third visit to the venue, after UFC 65 and UFC 73.

Dan Henderson: Daniel Jeffery Henderson (born August 24, 1970) is an American former mixed martial artist and Olympic wrestler, who last competed as a middleweight in the Ultimate Fighting Championship.  He was the last Strikeforce Light Heavyweight Champion and was the last Welterweight (80 kg ) and Middleweight (95 kg ) champion of Pride Fighting Championships.  Additionally, Henderson was the Brazil Open '97 Tournament Champion, the UFC 17 Middleweight Tournament Champion, the Rings: King of Kings 1999 Tournament Champion and the Pride Weltwerweight Grand Prix Tournament Champion.  During his career, Henderson also challenged for the UFC Middleweight Championship (2x), the UFC Light Heavyweight Championship and the Strikeforce Middleweight Championship.  He was the first mixed martial artist to concurrently hold two titles in two different weight classes in a major MMA promotion.  At the time of his retirement after UFC 204, he was the oldest fighter on the UFC roster.  Known to be one of the greatest mixed martial artists of all time having defeated a total of seventeen MMA world champions across four major MMA promotions (UFC, PRIDE FC, Strikeforce, and RINGS).

UFC 134: UFC 134: Silva vs. Okami, also known as UFC Rio, was a mixed martial arts (MMA) pay-per-view event held by the Ultimate Fighting Championship on August 27, 2011 at the HSBC Arena in Rio de Janeiro, Brazil.  The event was the second that the UFC has hosted in Brazil, since 1998's UFC 17.5: Ultimate Brazil.  UFC 134 was awarded the 2011 event of the year by Sherdog.

Mark Coleman: Mark Daniel Coleman (born December 20, 1964) is a retired American mixed martial artist, professional wrestler, former NCAA collegiate wrestler and former Olympic amateur wrestler.  Known as The Hammer, he was the UFC 10 and UFC 11 tournament champion, the first UFC Heavyweight Champion, and the Pride Fighting Championships 2000 Open Weight Grand Prix champion.  At UFC 82 Coleman was inducted into the UFC Hall of Fame.  At the age of retirement he was taking 150,000 USD salary per year.

Grand Est Open 88: The Grand Est Open 88 (previously known as the Open 88 Contrexéville and the Lorraine Open 88) is a tournament for professional female tennis players played on outdoor clay courts.  The event is classified as a $100,000 ITF Women's Circuit tournament and has been held in Contrexéville, France, since 2007.

Supporting paragraphs: UFC 88 Philips Arena
Answer: 1999