The Millenium - DH and several colleagues spent eighteen months scrutinising every line of every program involved in running the systems that brought an essential utility to the public. They were checking in case one line in tens of thousands might have contained an electronic instruction that didn't take into acount the fact that a second after 23 hours, 59 minutes and 59 seconds of the last day of 1999 would be 0 hours, 0 minutes, and 0 seconds of 2000 which would not have been allowed for in a program written some time previously when computers were less powerful and had less storage built into them
Had there been such a line, and had they missed it, the control systems would have failed, the machinery closed down, the distribution stopped dead. There would have been the mother of all power cuts, affecting homes, hospitals, life support systems, factories, schools, transport, traffic lights, airport control towers, you name it. The country would have ground to a halt, production halted, and lives would certainly have been lost.
Are the majority of us still here and unscathed? Yes, we are, because something was done about it. Not in panic, but as a planned exercise in finding and dealing with the possibility of disaster. It wasn't "Project Fear" It was "Look it full in the face and know what you have to deal with"