The Y2K computer bug was an important point in human history whose significance will not be appreciated for many years.
The Y2K bug was the first major technological crisis of the Information Age. Computers that weren't programmed to accept a four-digit year malfunctioned when 1999 turned to 2000. If not corrected, the bug could have shut down the global economy for months, and caused massive humanitarian crises, but by late 1999 critical infrastructure had been largely repaired.
In late 1999, ignorance of how the bug worked prompted fears of apocalypse at midnight January 1, 2000, which were compounded by a worldwide terrorist threat and extreme religious beliefs. When the expected catastrophe did not immediately occur, people around the world celebrated.