Question: UFC 123 was the first Detroit UFC event since the event held on what date?

Context paragraphs:
UFC 101: UFC 101: Declaration was a mixed martial arts pay-per-view event held by the Ultimate Fighting Championship (UFC) on August 8, 2009 in Philadelphia, Pennsylvania.  It was the first ever UFC event held in Philadelphia.  The event featured the second title defense of Lightweight Champion BJ Penn against Kenny Florian, and a non-title Light Heavyweight bout for Middleweight Champion Anderson Silva against former Light Heavyweight Champion Forrest Griffin.

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.

UFC 123: UFC 123: Rampage vs. Machida was a mixed martial arts event held by the Ultimate Fighting Championship on November 20, 2010 at the Palace of Auburn Hills in Auburn Hills, Michigan.  It was the first UFC event in the Metro Detroit area since "UFC 9".

UFC Live: Sanchez vs. Kampmann: UFC Live: Sanchez vs. Kampmann (also known as UFC on Versus 3) was a mixed martial arts event held by the Ultimate Fighting Championship that took place on March 3, 2011, at the KFC Yum!  Center in Louisville, Kentucky.  The event was broadcast on Versus in the U.S. and Rogers Sportsnet One in Canada.  This was the first UFC event to be broadcast in 3D.

UFC Live: Jones vs. Matyushenko: UFC Live: Jones vs. Matyushenko (also known as UFC on Versus 2) was a mixed martial arts event held by the Ultimate Fighting Championship on Sunday, August 1, 2010.  Originally scheduled to take place at the EnergySolutions Arena in Salt Lake City, Utah, the UFC was forced to move the event to a different venue due to low ticket sales.  On June 14, 2010, the event was moved to San Diego, California to be held at the Valley View Casino Center.  The event was the second UFC event to be broadcast on Versus; the first being .

UFC 30: UFC 30: Battle on the Boardwalk was a mixed martial arts event held by the Ultimate Fighting Championship at the Trump Taj Mahal in Atlantic City, New Jersey on February 23, 2001.  UFC 30 was the first UFC event under the new ownership of Zuffa, LLC, and also the first UFC event since UFC 22 to see a home video release.

UFC 9: UFC 9: Motor City Madness was a mixed martial arts event held by the Ultimate Fighting Championship on May 17, 1996, at the Cobo Arena in Detroit, Michigan.  The event was seen live on pay per view in the United States, and later released on home video.

UFC 78: UFC 78: Validation was a mixed martial arts event held by the Ultimate Fighting Championship (UFC), that took place on November 17, 2007 at the Prudential Center in Newark, New Jersey.  "Validation" was the first UFC event held in New Jersey since June 4, 2005's "UFC 53: Heavy Hitters" in Atlantic City.

UFC 70: UFC 70: Nations Collide was the second UFC event held in the United Kingdom, and the first in Manchester on Saturday, April 21, 2007.  "UFC 70" was also only the seventh UFC event held outside the United States, and the first since "UFC 38".  The card was broadcast live on pay-per-view in the United Kingdom and Ireland on Setanta Sports.

UFC 127: UFC 127: Penn vs. Fitch was a mixed martial arts event held by the Ultimate Fighting Championship on Sunday, 27 February 2011 at Acer Arena in Sydney, Australia.  Due to the time zone difference it aired live on Saturday, 26 February in North America.  This was the second UFC event held in Sydney, following the sold-out UFC 110 in 2010.

Supporting paragraphs: UFC 123 UFC 9
Answer: May 17, 1996