Well, while 31 Oct 2005 was the 20th anniversary of the 1st meeting of the CD-ROM Ad Hoc Advisory committee (some have called this the High Sierra Group), which produced the High Sierra Group Proposal, the seed of ISO 9660, which seems to have had a significant impact.
Well, 2 June is the 20th Birthday of the High Sierra proposal as that was the day I sent out the finished proposal.
To this day, I am haunted by my forgetting to change the date on the paper, so folkes may think that the birth date was 28 May 1986, but it was 2 June 1986.