Apocalypse

The Apocalypse (世界崩壊) —also referred to as the Day of Lavos (ラヴォスの日)— occurs in 1999 AD at 1:24 when Lavos is set to destroy the world in. Three individuals from other time periods arrive to defeat Lavos, preventing the Apocalypse from occurring.

Original timeline
Lavos erupts from underground and sprays explosive spines into the atmosphere, which fall on the entirety of the planet's crust and wipe out almost all of life and human civilization. The planet becomes practically uninhabitable, and humans must rely on what little food they can find to survive, as well as use Enertrons to rejuvenate themselves. Even the landmasses seem to have changed shape.

Many of the robots that "survive" the Apocalypse come under the control of Mother Brain and begin to take over the world.

Altered timeline
Three time travelers appear to stop Lavos from destroying the world. They defeat Lavos's crust and then move into its innards to defeat "Inner" Lavos and then the Lavos Core. Thus, the Apocalypse is prevented.

Appearance
1999 A.D. has a futuristic metropolis appearance. It is similar to Present other than the fact that the cities are in domes, and ruins cover the landmasses.

Accessing 1999
1999 AD is the only major time period that is not directly available to explore. If the party travels to this time, it is forced to engage Lavos in battle. The party can access Lavos via a bucket in the End of Time that acts similarly to a regular Time Gate, via the teleporter to the right at the Millennial Fair, via the Epoch, or by defeating Queen Zeal at the end of the Black Omen. If accessed via the Epoch after it has been outfitted with wings, the vehicle crashes into Lavos, entirely avoiding the battle with its shell, but this removes the save point and Time Gate inside Lavos.

Relevance to
Upon reaching access to the Dead Sea, Serge and the party discover a dimensional distortion consisting of various destroyed futuristic cities surrounding a large tower made of fused buildings, all laying with in a sea frozen in time.

It is later revealed that the area is made from the alternate future where Lavos was not stopped from destroying the world and succeeded into causing the Apocalypse.

Game Over
A unique game over sequence is shown if Lavos defeats the party. The sequence shows Lavos destroying the world, and the perspective then shifts to a lab in which three people, a director, a supervisor and an operator, are witnessing the coming apocalypse. Locations all over the world are indicated with red dots and labels, showing that they have been destroyed. The lab itself begins to crumble; the director commands the other two to leave immediately and stays, being crushed under the building.

The sequence then shows the planet in its entirety (as seen from space). It goes gray and a message appears: "But... the future refused to change." In the DS version, it says, "In the end the future refused to change."

Trivia

 * Due to its unplayable nature, little is known about 1999 A.D. From 2300 A.D., it can be deduced that the Guardia line has some amount of control over Arris Dome, as Doan lives there in 2300.
 * Only about a quarter of the 1999 world, the quadrant in which Lavos erupts, is actually complete. There is a video showing that 1999 A.D.'s map is explored. Based on the "location" of the domes, it can be assumed that the Guardia Kingdom eventually relocated into a large Truce-Guardia dome; likewise, Porre relocated into a similar-sized dome. In addition, on the "central" continent, approximately where Medina is, one can see a very technologically advanced facility which is different from everything else. It could be assumed this is the location of Chronopolis from . However, since the developers never wanted anyone to explore this area (and it is accessible only via codes), the nature of these domes and their locations is unverifiable and cannot be taken as canonical.
 * Many intercontinental roads still appear on the map, though they are damaged. Lavos may have caused this.