Actually, it's a date from one of the old Maya calendars, in what archaeologists call the Long Count, which indicate a continuous sequence of dates from some presumably mythical starting point somewhere around 3100 B.C. This particular date, 126.96.36.199.0, is the one which is supposedly coming up very shortly, at least according to one particular alignment of the Maya sequence with ours. Other historians give different correlations, and this particular book, the ninth installment of the Saga De Bellis Stellarum, uses a correlation which makes this end-of-the-baktun fall in December of 2015 - on the birthday of John Collins, no less!
So, if you are curious to hear how the world "ends"... you may wish to check it out. You can rest assured that there are four more installments to come, so you need not look so tragic... but do recall what Chesterton said:
Every short story does truly begin with creation and end with a last judgment.The Saga is, of course somewhat more lengthy than a short story... but we shall defer discussion of the other matters to a future time.
[GKC The Everlasting Man CW2:379]
Oh yes, if you want to get the book, or find out more, go here.