Time is almost as important to our speaker as his long-lost love is, but it drives him a little bit crazier. Time goes back and forth, from past to present to future, and the speaker can move through time like the Terminator. Well, maybe not quite like that. The point is, time plays two roles in "Piedra de sol"—one, the big, bad, unstoppable march to death (sad); and two, a kind of loopy, out-of-control chaos.
The only way to escape time is through death, according to the poem.
The only way to escape time is through love, according to the poem.