Shawn Michaels and Triple H were real life best friends. Chyna was Triple H's manager and at some point in time became his real life girl friend.
D-X Phase 1
8/11: Shawn Michaels beat Mankind due to the help of Triple H, Chyna, and Rick Rude
8/18: Triple H and Shawn lost to The Undertaker and Mankind in their first match as teammates.
9/7 Ground Zero: The Undertaker and Shawn Michaels fought to a no contest
9/20 One Night Only: Shawn Michaels beat Davey Boy Smith to win the European title
9/22: Cactus Jack made his WWF debut and beat Triple H.
10/5 Bad Blood: Shawn Michaels beat The Undertaker in the first hell in a cell match
10/6: Shawn and Triple H show footage of the infamous MSG curtain call from a few years earlier. Bret Hart called Shawn a degenerate. Triple H beat Bret by count out and Shawn picked his nose with the Canadian flag.
10/13: Shawn uses the words Degeneration X for the first time.
11/3: Shawn and HHH don face masks with windshield wipers to mock Commissioner Sgt. Slaughter’s flying saliva
11/9: Shawn beat Bret Hart to become WWF Champ in the infamous Montreal Screwjob
11/17: Rick Rude left the WWF because of what was done to Bret. Due to RAW being taped, he became the first man to ever appear on both RAW and Nitro the same night.
11/24: Shawn recreates the Montreal Screwjob with a midget version of Bret Hart. Jim Neidhart is named the newest member of D-X only to have them turn against him later that night.
12/1: Triple H beat Jim Neidhart and then spray painted WCW on him
12/7 In Your House D-X: Triple H beat Sgt. Slaughter in a boot camp match and Shawn lost to Ken Shamrock by DQ
12/8: D-X plays strip poker in the ring.
12/15: The Legion of Doom beat Shawn and HHH by DQ when The New Age Outlaws (The Road Dogg and Billy Gunn) came out and shaved one of Hawk’s two mohawks. This was the first time that The New Age Outlaws associated themselves with D-X
12/22: Sgt. Slaughter forces Shawn to fight HHH. Shawn lays down for Hunter and Hunter wins the European title. That night, Shawn, HHH, & Chyna mooned the crowd to reveal Merry X-Mas painted on their flesh.
1/18: Shawn beat The Undertaker in a casket match. During that match, Shawn suffered a severe back injury that would lead to him missing 5 years.
1/26: Goldust subbed for Triple H and lost the European title to Owen Hart
3/2: Mike Tyson is revealed as the newest member of D-X
3/16: Triple H regains the European title from Owen
3/26: WrestleMania public workout featured D-X tie Austin to the ropes and Mike Tyson kiss Austin’s forehead
3/29 WrestleMania 14: Shawn lost the WWF title to Steve Austin when Mike Tyson made the 3 count. After the match, Tyson punched Michaels and tore off his D-X shirt to reveal an Austin shirt underneath
D-X Phase Two
3/30: Triple H is the new leader of D-X and announces the new members X-Pac and The New Age Outlaws. That night The NAO beat Cactus Jack & Chainsaw Charlie to win the tag team titles.
4/27: While in military garb, D-X drives an army tank to a WCW event and declares war.
5/11: D-X invades the CNN center and WCW headquarters
5/25: HHH skywrites over a WCW event WCW S***s and S**k It
7/6: D-X mocks the Nation of Domination in one of the most famous segments in RAW history
7/13: NAO lose tag team titles to Kane & Mankind
8/30 SummerSlam: HHH beats The Rock to win the I-C title & NAO beat Mankind & Kane to win the tag team titles
9/21: X-Pac wins European title from D-Lo Brown
10/5: X-Pac loses European title to D-Lo Brown
10/12: Triple H stripped of I-C title due to injury
10/18: X-Pac wins European title from D-Lo Brown
12/14: D-X redo their NOD parody but this time they skewer The Corporation
12/14: NAO lose tag titles to Ken Shamrock & Big Bossman
1/25: Royal Rumble – Chyna turns against D-X
2/15: X-Pac loses European title to Shane McMahon
3/15: Road Dogg beat Val Venis for I-C title
3/28 WrestleMania 15: Chyna turned on Kane during his match with Triple H to rejoin D-X. Later that night, Triple H and Chyna turn against X-Pac and join the Corporation. While D-X stays together it is no longer an elite group. For a brief time, Kane and Tori are parts of the group. The remaining members of the group eventually feud with each other over the D-X name.
D-X Phase 3
Late 99 – The group reforms with Triple H as the leader right before the wedding of Stephanie and Triple H. Once HHH marries Stephanie, he leaves the group to form the McMahon-Helmsley era. D-X becomes allies of that group for a few months.
D-X Phase 4
2006 – After feuding since 2002, Triple H and Shawn Michaels put their differences aside due to their mutual hatred of the McMahon family. All future D-X timeline events can be found on the timeline pages for Shawn and Triple H.
Sources: Onlineworldofwrestling.com, thehistoryofwwe.com, PWI Almanac, & WWE.com