After playing both Chrono Trigger and Chrono Cross I started to think if there was only one sole timeline in the Chrono universe, where Lavos did crash into the Earth, caused an Ice Age, destoryed Zeal while sending Janus, Melchior, Gaspar and Belthasar into their respective future dates. The reason for only one timeline? Not once at any point in the timeline where a point in history was changed, Janus and the three Gurus vanishing from 12000BC only to appear at different time periods, all after 12000BC, is part of the unchanged original timeline. In theory, moving forward in time makes you part of history, moving backward in time changes it. And there were no changes in history... Until the Entity decided to send Marle from 1000AD to 600AD. With that in mind, that action alone would've caused a dimension to divert from the original timeline where Leene was supposed to be found without any interruption. (If you want to get technical about it, then perhaps right after Marle was sent back in time everything from 600AD and onward should've been sent to the Darkness Beyond Time? But I won't talk about it now.)
This is my imagined original timeline from past to end of time, uninterrupted, most of it explained by dialogue from Magus at North Cape right after the fall of Zeal;
Before 12000BC - No recorded history before 12000BC from the perspective of the original timeline. Sometime before 12000BC, we know that Lavos crashed onto the Earth. Sure we all know that it was in 65000000BC, but take in mind this was after Crono and co. traveled back into that distant past. We know it crashed, but not sure when during the original timeline. We(the player and the humans of the game) do know that it is an entity that is with great power, but only we the player's perspective, know that it came from outer space. There was an Ice Age that started and we assume(like what happened to our own history) that dinosaurs died.
12000BC - Mammon Machine is completed and shortly afterward Lavos is summoned. Janus and the three Gurus are forced sent to future time periods, from Magus' where it becomes part of the original timeline. Schala(maybe?) uses her magic to escape death(with Zeal?) from Lavos. Magic eventually became extinct for use by humans except for wizards(as told by Spekkio) but you never saw them except for that freaky dude with no chest body in the tent at the Millenial fair. It does not seem
12000BC~580AD(maybe?) - Janus appears in the middle ages. His absence for the last approx. 12600 years is part of the original timeline.
Whenever Janus appeared~600AD - Janus becomes Magus under the supervision of the Mystics, as told by Magus.
600AD - Magus' army wage war on the kingdom of Guardia, the kingdom of Guardia won, as told by some dialogue before going into the Millenial Fair at the start of the game.
12000BC~1000AD - Melchior appears in 1000AD shown from the scene in Magus' story. His absence of exactly 13000 years is part of the original timeline since he traveled from the past.
1000AD - Guardia is in a time of peace and prosperity. The Millenial Fair is organized. Marle mysteriously disappears from the timeline. (Not really sure if I should put Crono and Lucca disappearing as well in the original timeline, since technically them going back in time would be already part of the changed timeline from the moment Marle appeared in 600AD.)
1000AD~2300AD - From the original timeline's perspective, we do not know if the Day of Lavos occured in 1999AD. Remember that 1999AD definitely happened after Crono and Lucca saved Leene and brought Marle back with them to 1000AD. But the apocalypse definitely did happen because...
12000BC~2300AD - Belthasar appears in 2300AD shown from the scene in Magus' story. His absence of exactly 14300 years is part of the original timeline since he traveled from the past. The era appears to be in ruins. Something at one point in time that shook the world made civilization in shambles.
12000BC~End of Time - Gaspar appears at the End of Time, whether it be from the perspective of humans or something greater or lesser, shown from the scene in Magus' Story. He just vanished from history and never returned is now part of the original timeline.
...Does this make sense on how this original timeline would be envisioned? Before Marle gets sent back in time? It always hurts my head talking about this game. I got very technical. lol
Now this is the timeline after Marle gets sent back in time;
Everything up until 600AD - Remains the same.
600AD - Leene is at one point captured by mystics and a search party is sent. Search party finds Marle whom they mistakenly take for Queen Leene of Guardia.
600AD~1000AD - No idea what happens here, Marle might act tomboy and eventually leave Guardia for a way back home and never realizing that she's in the past; The real Leene might eventually be found; both, one or the other, none, or something entirely different might happen; We just don't know. Looking at a Chrono Cross angle, the rest of original timeline would get dumped into the Darkness Beyond Time.
1000AD - This era should now be different, then having a Marle existing in this time period, since the one from the original timeline lived and died of old age(realistically saying) nearly 400 years ago.
1000AD~End of Time - Unknown what happens.
...Does this difference make sense? If any of you had played Chrono Cross, Miguel makes you realize that every choice you make creates a future. After Marle is sent back in time, Crono, Lucca and everyone after 600AD should be sent to the Darkness Beyond Time? This made me think, what if the Darkness Beyond Time is only a perspective of the Chrono series characters, to which they cannot return or live through the other future had they had chosen another path in life? Because Crono and Lucca still seem intact, 1000AD still seems normal after Marle appearing in 600AD. I could go on and keep re-explaing each timeline everytime the Chrono crew move back and forth through time, but maybe I'll do it another time.
...and that was for how I believe there was only one sole timeline before the Chrono Trigger adventure began... I went off topic from my own topic lol, but discussing Chrono-related stuff just does that.
Anyhow back on topic, I do think that Lavos did indeed crashed into the Earth at 65000000BC and existed in all timelines. I mean heck, some things have survived throughout the ages even with Lavos' influence. There was still a dinosaur that existed in 600AD, the Sun Palace existed in 2300AD from the kingdom of Zeal, and the sun keep, that hardly ever moved. Why couldn't the Reptites survive even with Lavos crashing? The Tyrano lair survived. Maybe in the dimension that Crono and co. obtain the rainbow shell the Reptites weren't so lucky in surviving, maybe the Rust Tyrano ate them all? LOL... Who knows if in the Reptite/Dragonian dimension if the Reptites had won the prehistoric war against the humans? Maybe the humans won at first? Who knows?