He has lost track of the apocalypses he has lived through; somehow they come once a generation or two, a wash of fire, of war, of pandemic, of collapse. They blur together, the deaths, the dead, and the dying, a bright flash, a sharp tang, the smell of smoke that lingers in his clothes for decades. He cannot escape the stench of burning flesh, somehow.
But after the end of the world, the birth of the new: fields of poppies, new cities, old rags shed for flash clothes, food for all, race sex and class overthrown for a time, a pulse of realization of what could be, should be. That, too, blurs together. The New Jerusalem has come a dozen times and more, and been overthrown; he has picked lapis lazuli from the gates time and again and left them strewn in stream a continent away, just to mess with the archaeologists. Figure that out, schmucks.
After the twelfth century he stops looking over his shoulder; the millennium is never coming, the clock is never stopping, the road will never end. World begets world, forever and anew.