In a 1993 Rolling Stone interview Garcia said, "the date that holds significance for me is 2012. That's [writer and self-described expert in 'the ethnopharmacology of spiritual transformation'] Terence McKenna's alpha moment, which is where the universe undergoes its most extraordinary transformations. He talks about these cycles, exponential cycles in which, in each epic, more happens than in all previous time. Like he talks about novelty, the insertion of novelty into the time track. His first example of novelty is, say, the appearance of life. So the universe goes along, brrrrmmmmm, then all of a sudden, life appears: bing! So that's something new. Then the next novelty is, like, vertebrates. Then the next novelty might be language -- that sort of thing. They're transformations of a huge kind, gains in consciousness. So he's got us, like, in the last forty-year cycle now -- it's running down, we're definitely tightening up -- and during this period, more will happen than has happened in all previous time. This is going to peak in 2012. He's got a specific date for it, too -- maybe December some time, I don't remember. But that moment, at the last 135th of a second or something like that, something like forty of these transformations will happen."
Also, there are blurbs from several GD members for some of the aforementioned Terence McKenna's books (I think most of the band members were reading The Invisible Landscape back in the mid-70s ):
The Invisible Landscape: Mind, Hallucinogens and the I Ching
"One of the most mind boggling books I've ever read." --Jerry Garcia
Food of the Gods
"McKenna is a wild man, probing the depths of the great mysteries of the mind. He asks big questions, he rides the Edge. He's an explorer, a circumnavigtior of human consciousness. Terence is on to something" --Mickey Hart, The Grateful Dead
"How the Magellan of mentats put his mind and body on the line and discovered the source of consciousness, the end of history, and the factors that govern the ingress of novelty into our world. If you've been there, this book will take you back; if you haven't, get ready." --Phil Lesh, The Grateful Dead