midnight on Jan 1, 1970 (which was somewhat arbitrarily chosen).
well not so much, as far as I remember the first end-user computers became available in 1971 or 1972 or something, and the internet also underwent some rapid developments in that time, so the date has a certain reasoning to it.
well there have been mass extinctions before, the most notable maybe oxygenation catastrophe , mainly caused by photosynthetic life.
And it represented a major breakthrough for life on Earth, so i doubt that this one is an irreparable crisis.