Would the fact that "Live Scenes" was released on 9/11/01, and that they had to recall it and change the cover art because of the terrorist attacks be a good example of what you're looking for?
Might be a bit obscure but that was also the day in the studio that they were planning on mixing a song called Conflict at Ground Zero which they tactfully decided to change the name to The Great Debate.
I don't believe they said they were planning to work on that specific song on that day, though that was the original title.
But that was the first day that James was supposed to go to start recording vocals for the album.
Let's see...
June 15, 1951 - Charlie Dominici is born
November 4, 1956 - Jordan Rudess is born
May 5, 1963 - James LaBrie is born
August 25, 1966 - Derek Sherinian is born
January 24, 1967 - John Myung is born
April 20, 1967 - Mike Portnoy is born
July 12, 1967 - John Petrucci is born
August 10, 1967 - Chris Collins is born
July 18, 1988 - Majesty enter Kajem Studio to start their recording sessions for When Dream and Day Unite
October 7, 1988 - The band formerly known as Majesty performs a CMJ music showcase concert where they announce their new band name: Glasser
March 6, 1989 - When Dream and Day Unite is released
June 9, 1990 - Steve Stone performs with Dream Theater for the first and last time at the Sundance in Bay Shore, Long Island
October 14, 1991 - Dream Theater moves into Bear Tracks studio to record Images and Words
June 2, 1992 - James LaBrie performs for the first time with Dream Theater at Hammerhedz in Elmont, Long Island
June 8, 1992 - Dream Theater opens for Iron Maiden at the Ritz Club in New York City
July 7, 1992 - Images and Words is released
April 23, 1993 - Dream Theater record their Live at the Marquee concert
May 1994 (no day specified) - Awake Sessions begin at One On One studios in North Hollywood
October 4, 1994 - Awake is released
October 20, 1994 - Waking Up the World Tour kicks off at The Strand in Providence, Rhode Island
December 30, 1994 - James LaBrie has a food poisoning accident that impairs his voice for years to come
January 14, 1995 - Dream Theater begins their tour in Japan to promote Awake
September 19, 1995 - A Change of Seasons EP is released
June 2, 1997 - Falling Into Infinity sessions begin at Power Station Studios (Later to be renamed Avatar studios)
September 23, 1997 - Falling Into Infinity is released (the book states October, but doesn't list a day. Wiki says Sept. 23)
October 26, 1999 - Scenes From A Memory is released
February 4, 2000 - Dream Theater's concert at Palace Theater, Los Angeles, gets shut down by the police and the fire department right in the middle of The Spirit Carries On
August 30, 2000 - Metropolis 2000: Live Scenes from New York is recorded at the Roseland Ballroom in New York
October 16, 2001 - Someone already mentioned the 9/11 album cover insicent. This was the date the live album was re-released with the new cover
Phew... That's all I got for now.