I'm still confused, 14 years later...
The "Antique Code Show" article that this story links to, giving the Reg's 20-year retrospective on Doom, was published Wed 23 Nov 2011, and opens with the words "id Software’s Doom – the definitive first-person shooter – is 20 years old today. It was uploaded to the University of Washington’s servers at midnight, 10 December 1993"
Now is it just me, or was there some very odd date-calculation going on there?
Did we move away from the Gregorian calendar at some point in the intervening period, losing several days again?
A pint for all concerned in this latest endeavour, nonetheless.