The Last Day of the World
From Chrono Wiki, a database for the Chrono series that anyone can edit
"The Last Day of the World", also known as the "The Final Day of the World", is a track composed by Yasunori Mitsuda for the game Chrono Trigger. It is the second track on the second disk from the original soundtrack. First played in basement of the Arris Dome when the party agrees to stop Lavos from destroying 1999 A.D., the track appears again atop Death Peak, when the party revives Crono, using the Chrono Trigger.