DS version specific changes made "later" to Time-Space.
For clarity, this article contains unmarked spoilers.65 Million B.C. aka Prehistory
The Reptites are winning against the hairless apes known as humans. Ayla survives her battle with Azala and becomes Marle's ancestor. Lavos crashes into Tyranno Lair, killing Azala and plunging the world into a 64,988,000-year-long ice age. The Reptites cannot adapt to the environmental damage and die off; humanity ekes out a living for many millions of years to come.
Crono and crew beat Azala, and witness the descent of Lavos anyways. All of the other stuff happens too.
When the Epoch is recovered from Antiquity and the Black Omen arises, a portal to The Reptites' Lost Sanctum appears. It is unknown whether the Reptites here are the survivors from the fall of Lavos from the sky.
12000 B.C. aka Antiquity
Humanity survives the cold, and some actually discover how to tap into the energy that Lavos gives off; they use this for "magic." The Kingdom of Zeal is formed, with magic-users living lives of luxury in Floating Continents above the ground, while the magic-less are slaves to serve in caves in the bitter cold below. The Queen of this country has her Three Gurus fashion a device that will better tap the source of their power deep underground, the Mammon Machine. When it is completed, she becomes Drunk on the Dark Side and becomes a despot. The Gurus also develop other equipment from the Mammon Machine: a Pendant that can affect time and space as well as a Sword that can drain such power; however these are fused with dream spirits to prevent the same effect the Mammon Machine has. The Gurus and Queen Zeal's children, Schala and Janus, try to stop Queen Zeal, but she activates the Mammon Machine. Lavos twitches in its sleep, and the resulting space-time writhing sends Melchior to 1000, Belthasar to 2300, and Gaspar to the End of Time. Janus is sent to circa 570. The Ocean Palace stays underwater. Presumably Queen Zeal and Schala die.
Crono and company interfere with events, but Janus/Magus has already come back in time ahead of them and is expecting them. In an attempt to stop the first catastrophe from happening, he orders the Gurus imprisoned and attempts to maneuver the Queen so that he can attack Lavos when it comes forth. He fails at stopping Lavos (big surprise) and Crono is killed by the Eldritch Abomination as well. Queen Zeal survives and raises the Ocean Palace to become the Black Omen. Dalton is teleported off to who-cares-where by his own failed summoning Gate. Melchior is pulled into a time gate with Janus, and it is unknown where/when they turn up, as the circumstances are different from when it happened in the original timeline. Schala's fate is unknown...
Janus from the original timeline gets sent here. Janus is found by the Fiend Ozzy. Ozzy raises Janus to become the scourge of humanity and Janus goes along with this in order to gain sufficient power to learn how to summon and kill Lavos. Janus, now called Magus, rises to lead the Fiends against humanity. He kills Hero Cyrus and curses Glenn into becoming Frog, also destroying the Masamune which had a negative effect on his own Lavos-related powers. Right before the Fiends are about to win, Magus attempts to summon Lavos. All that is known is that he didn't succeed and Magus vanishes from history.
Crono and company beat back the Fiends and interrupt Magus's summoning ritual. Lavos twitches, Crono and company are sent to 65,000,000 B.C., and Magus is sent to Antiquity. At this point, there are two Maguses. One becomes the Prophet and is either killed by Crono's party or joins them, while the "original" vanished.
When the Epoch is recovered in Antiquity and the Black Omen arises, a portal to the Reptites' Lost Sanctum appears. The Reptites here are descendants of the Reptites of the Prehistory Lost Sanctum.
1000 A.D. aka the Present
Crono's time. Guardia is the primary superpower on the continent due to Porre to the south being too poor in resources due to the desert and its mayor being too miserly to care about development. The relationship between Guardia's king and princess is strained, but this means little in the long term. The Pendant of Dreamstone has been passed down throughout the Guardia family since Antiquity. Melchior from the original timeline gets sent here, where he sets up trade as a weapons merchant, and eventually repairs the broken Masamune.
Due to changes that Crono's party makes, Porre is now surrounded by lush forest, and has a philanthropic mayor.
When Lavos is slain, a Dimensional Vortex appears. It's revealed Dalton who had disappeared from Antiquity was sent to the Present. Dalton later leads the charge of Porre attacking Guardia leading to the Fall of Guardia in one of the endings.
1999 A.D. aka the Cataclysm
Lavos ascends and destroys the Earth.
Lavos does not destroy the Earth; Lavos has been destroyed.
2300 A.D. aka the Future
The destroyed Future. Only a handful of what once lived still exists; Lavos orbits the Planet and continues to feed off the dying embers, while propagating its spawn. Robots have become sentient and under the Mother Brain project are becoming the new dominant life-form. Belthasar arrives via Gate to this time period and, with what ruined technology he can work with, builds a time machine and some other stuff.
Lavos is dead; in one of the endings Robo is shown in the future Leene Square running into his girlfriend Atropos. Happy Endings all around.
When Lavos is slain, a Dimensional Vortex appears.
End of Time
Gaspar from the original timeline arrives here and eventually becomes the Old Man. Also, Spekkio gets here one way or another and sets up shop teaching strong time travelers to use magic.
When the three Dimensional Vortexes are cleared, a path to Time's Eclipse appears.
After Schala goes missing from the Ocean Palace in Antiquity after Lavos is awakened, she appears here in Time's Eclipse being absorbed into Lavos who appeared here after being slain. They combine into the Dream Devourer. A (second; if you have the "Prophet" Magus with you) Magus also appears here who futily tries to free Schala.