This is a write up of the PSO plotline, which spans all of the currently released games, except for Blue Burst (Episode 4 Section), This is a combination timeline + plot summary. With this guide, there's no more digging through tons of quests or the NPC guide to try and piece together the story you want!
This guide is color coded, to help distinguish all the different types of information.

Black Text: Facts taken from the games

Red Text: Assumptions made from information provided, along with the reasons it can be assumed.

Green Text: Dates provided directly by the games/Website

Blue Text: General Times/Dates

Purple Text: Something the game tells you through a message or NPC, or something you see happen in the game.

Pink Text: Info provided by "The Book of Hunters" (as translated)

Year/Game
Nef Miama's father buys the android Shino, on planet Coral. Nef Miyama is born and continues the Miyama sword fighting technique and legacy. Eventually, he passes it on to his own son, Zoke Miyama. Meanwhile, the governments and environment of Coral are in turmoil. With overpopulation war and pollution, the planet won't support the amount of citizens that exist for that much longer. The Dates for this are general, and assumed on the basis of the Miyama Family Members living to be about 80-100 Years old Each, and achieving fame at about the age of 30.

The government and the 10 Nation Alliance form a plan. The organization Black Paper is also involved in the decision. The Pioneer Project is planned to move the citizens of the planet to a more suitable world.

An asteroid from a distant galaxy passes by the planet. With the asteroid comes a strange new energy: Photon. The scientists of Coral study this new energy and form great new power sources and technologies using photon.

At an unknown point in this time period on Coral, the brilliant scientist Dr. Calus was working (probably with Osto) on a computer AI project. Supposedly he died before the project was finished...but apparently his work yeilded the AI also named Calus. Did he put a bit more then programming code into his work? Or did he just name his masterpiece after himself...This never got answered.

The Pioneer 1 ship begins to be constructed. Unmanned space craft are sent out into the universe to locate habitable worlds. One such planet, Ragol is found. The Asteroid is from or has passed by this planet. The organizations of Coral spacifically sought out the origin planet of the photon energy. The pioneer project goes there on purpose to mine and control photon. The government and various other organizations (such as the military and Black Paper) declare that world to be suitable to continue the Pioneer project.
Meanwhile: When Dr. Montague is 11 years old he joins up with Dr. Osto to research samples of D-cells that were brought back by the unmanned probes. Together, they invent MAGs. A mag is a core of D-Cells surrounded by metal plating. The D-Cells are kept in control by an "Emotional AI". This means any mag is actually a cyborg of some sort, because they are a fusion of living and mechanical tissue. This is also why spraying them with various medical items causes them to change their shape so drastically.
This is also why they can do the Photon Blast. The mag is able to absorb the energy from your photonic attacks on enemies, and also to absorb the pain from hits and turn it into photon. They had mags doing PBs on Coral, where the blasts did not take on a particular shape. The things you see in your PBs on Ragol look the way they do because the abnormal photon count, and D-cell count on Ragol is really high. The PB animals look like dark enemies, but with light color bodies. This is the influence of Ragol.
The MAG project is step one of project MOTHER.

Pioneer 1 launches carries with it most of Coral's top fighters, researchers and scientists and computer AI. Among the notable people on P1 are: Heathcliff Flowen the military leader and great warrior, Red Ring Rico Tyrell, daughter of Colin Tyrell, Dr. Osto Hyle the most brilliant scientist of Coral, and Mr. and Mrs. Graves a photon engineer and geneticist. Also along for the ride are the most powerful members of the military operation WORKS. Pioneer 1 brought 3 Computer AIs as well, Calus, Olga and Vol Opt. These 3 AIs were meant to assist P1 with research and were also step two of project MOTHER. When P1 lands, they immediately begin exploring the surface of Ragol using various robots and personnel. The travel time of P1 is disputed by the game/website AND books! How many years did it take?

Planet Ragol proves to be a paradise. The weather and environment is habitable and nice. The animals on the planet are friendly and docile. Researchers explore the various species living on the land and in the ocean. Scientists begin to set up bases all over the planet. A large research facility is built on Gal Da Val island which houses the computer AI Olga. Olga was not always in the SeaBed Facility. She was moved there at a later date, in hopes of controlling the body of HeathCliff. A robot building plant and factory/mine is set up underground on the main land. This facility houses Calus and Vol Opt, and is also home to Dr. Osto's first lab. A large dome is built in the forest to house supplies and a communication center.

War continues on Coral, weakening the 10-Nation Alliance.

Dr. Osto uses his underground lab to create a mutant life form, Beta 722. This creature started out as a small worm like animal, but grew out of control, and escaped, killing the scientists of Ostos Lab when they tried to move it to another tank. This creature became known as De Rol Le and Dal Ra Lie. It has the ability to self-replicate so there are any number of the creatures living in the underground sewers/waterways below the caves and the mines. This creature has tentacles which it uses to mutate other life forms and make them violent. It is responsible for the creatures in the caves.

Heathcliff Flowen discovers the Ruins. These ruins are actually not a part of an alien civilization, but rather a huge space craft sent from an unknown and distant world. This craft houses Dark Falz an evil entity, in search of the perfect body to use to bring evil into the universe. The alien civilization imprisoned this evil force inside a ship and sent it far away. It crashed on Ragol and was sealed there ever since. The military sends in an investigative team to explore the ship. Everyone dies. Heathcliff leads a second expedition with his men into the alien craft. Dark Falz awakens, and kills all of Heathcliffs' men. Only the commander survives, but with many wounds. Once Heathcliff leaves, the door seals again. Rico re-opens it.

He returns to the medical center of P1, and Dr. Osto attempts to help him. The wounds created by Falz are moving and alive. Osto is fascinated, and wants to conduct experiments. Flowen knows that he will probably die anyway due to his infections, so he makes a pact with the medical researchers: "If they tell P2 to stay away from the planet, which he now knows to be very deadly, he will give his body over to them to use for research." Dr. Osto agrees to this and takes Flowen away to their Gal Da Val research lab. Once Flowen is sufficiently mutated and isolated, Osto breaks the promise, and tells P2 to come to the safe 'paradise world'. Officialy, it is stated that he "Dissappears". Central Dome is completed.

The likely reason for all the experimentation and innuendo that the government/organizations HINTED that they went to Ragol on purpose would be to purposely find the space ship and its contents. Osto's experiments were most likely trying to create a "Super Soldier" of some kind for the military to use. This part is never directly stated in the game, but it is repeatedly hinted at by several NPCs, quest plots and data files. There are many government and military science labs, including Ostos' and WORKS. If you notice the Deldepths, and ESPECIALLY Il gils found in the SeaBed/Towers, they are very Human in form and function, which was Ostos' Goal. The bad doctor continued to do D-Cellular experiments on various animals he found.

Ostos' greatest masterpiece, the body of Flowen, began to get out of control in the lab on Gal Da Val. In an effort to maintain control over the huge creature, Osto merged it with the AI computer he had been provided for the island lab: Olga. This merger created the infamous Olga Flow. When that failed to bring the creature under their control, the scientists dumped it down a huge pit into the failed experiment area.

Believing the message received from P1, P2 is launched and heads for Ragol. Meanwhile, the animals begin to become violent toward the P1 colonists. Rico begins investigating.

The government of P2 finds columns on the surface of the planet marked in alien writing with red, green and blue symbols on them. There is no real intelligent life on Ragol to have built the columns....so they must have come from the ship. These columns are what seals the ship's door, which is located beneath the No Mans Mines. Rico studies and unlocks the columns, in her quest for knowledge. The government tells a lie to the citizens and hunters. It says they were built to commemorate the landing of P1, but Rico sees through this, as the columns are obviously much older. Through her recorded messages, you can follow her progress as she moves closer to the answer to the mystery.

Dark Falz has no physical form, so it is seeking the perfect body to inhabit. Consequentially, it lures the great hunter, Red Ring Rico to it once she touches all three unlocking columns. It also wreaks a little mental havoc on the powerful android assassin, Kireek, much later on. Falz captures Rico deep within the space ship, and takes over her body. It mutates her into a huge morphing monstrosity and waits for more people to come. Anyone who arrives at the chamber where Falz stays, sees what Rico imagines, at first: a pretty garden glade with a harmless looking stone monument. After Rico opened the door, it closes again, and you have to open it to get into the ruins. If Falz is killed on a difficulty above normal, you can see Rico's spirit as it is freed from imprisonment within the evil life form.

On the way to Ragol, Montague continues with Project MOTHER and builds Elenor and Ult. MOTHER 00 and MOTHER 01. These two androids have D-Cell cores, much like mags. This is why Ult freaks out around high levels of photon and D cells in the quest Soul of Steel. Ult had a special chip inside of her, and was always locked away in a tube in his lab, as she was less stable then Elenor. Elly Person begins communicating with the AI Calus at this time, as he pretends to be a human.

When the P2 ship arrived in orbit around Ragol, and attempted to establish a communications uplink with the central Dome Communications center, a disaster occurred. A huge explosion of energy appeared around the dome on the surface of Ragol. This explosion was caused by Dark Falz as it killed/absorbed everyone from P1. There were only 4 surviving people left from P1. One was Heatcliff Flowen in his mutated state, the second was the AI Vol Opt, the third was Red Ring Rico, also in a mutated state, and the other was a single remaining sane AI, Calus.

Pioneer 2 decided not to land, once they saw the explosion. Instead, P2 remained in orbit to keep the citizens safe. Ever since, hunters have been investigating the surface of the planet. On special request...hunters are sent down by Principal Tyrell to find his missing daughter.

This marks the end of Episode One

Once Dark Falz was defeated, everyone thought they could land the ship safely on the surface. This proved to be untrue. The planet was still very unsafe for civilians. The science labs knew this, and kept sending hunters down to explore. Instead of being under the jurisdiction of Tyrell, hunters now follow the chief of the Lab Natasha Milarose. She used to be an underling of Tyrell, and was very difficult to work with. From the lab, Natasha directs hunters and researchers on the planet's surface. One day, a message arrives in the lab from the surface of Ragol. It appears that someone is still alive from P1 on Gal Da Val island. After testing in the latest VR simulators (space ship and temple) hunters are allowed to go to the dangerous island.

Gal Da Val island is home to more violent creatures, just as the forest of the mainland was. Also inhabiting the island is another of Dr. Ostos' experiments gone awry. This time, he used an animal, and created the Gal Gryphon. Also on Gal Da Val are two towers, East and West. At the top of one of them, Osto had nearly completed the MOTHER vortex. This mysterious swirling area was meant to give a physical body/humanoid form to the three super powerful AIs that P1 brought along. The AIs were meant to learn about the world, then willingly return to the MOTHER vortex and be formed. That is why you see human shaped diagrams on the walls in the tower in Seat of the Heart. The diagrams were there for the form of Delta, as well as the AIs. They were still trying to create Super-Soldiers.
There are also message recordings of Flowen left behind in small computer outposts scattered over the island terrain. These message logs are the source of most of the facts in Episode II. The messages directly to P2 are not from the island surface though, they are coming from the Sea Bed research facility. The messages are from Flowen himself. He has sensed the death of Falz/Rico and uses the AI Olga part of himself to contact P2. It is assumed he is trying to summon people there to both warn them about the prescience of the evil on Ragol, and also to end his own life.

10 Years later: The Time Period of Blue Star Memories

Once Falz and OlgaFlow are killed, there is a sharp decline in the monster population. Without the influence of evil on the surface of the planet, and the rogue AI Vol Opt dead, the animals don't act as violently and the machines of P1 stop going haywire/more stop being built. The game does not directly TELL you that the deaths of Falz, Vol Opt, Dal Ra/ De Rol, and Olga are responsible, but what else could it be? This decline in monsters leads to a decline in people who can hunt them for money. Nef Miyama, having outlived his own son, is once again training people in the Miyama Sword Fighting Technique. This time, his students are Wilm Break and Orland.

A Coup against Dol Grisen fails. Break and Orland get their Hunters Lisences, and become famous throughout Pioneer 2.

Coral recognizes Pioneer 2/ Ragol as a separate state from the home planet.

Break Dissappears, presumably due to OPSS involvement, and probably ends up down on Ragol with the forming prototype of the ARKZ movement.

Orland begins working with the Government of P2, but behind the scenes. He helps in the arrest of Han Walt, a man responsible for the OPSS massacre. Orland is also recognized as the youngest human to reach Cmode rank Gi-Ei. It is noticed that Break is missing.

Blitz, Kranz's father as well as several other hunters continue to explore Ragol. He discoveres by mistake, The Germ. Blitz is infected, as well as his team mates. When they return to P2, the hospital and lab workers who attempt to help them are all infected and killed. Only Blitz manages to survive, and from his data, the scientists create the start of CARD technology. The germ allows large things to be materialized from small card like objects. Efforts commence to find the source of the Germ, in order to obtain greater amounts of it to create more effective CARDS. (such as cards that will hold entire armies, or space ships.)

The ARKZ movement is formed due to the discontent of citizens with the P2 government. Cards containing weapons and shields are distributed to a few select hunters. The whole CARD technology is meant to be kept a secret by the military, but news leaks out over the internet. The Arkz begin to battle the Hunters.

Episode 3 Begins

--

Phantasy Star Zero

The plot of PS0 takes place back on Coral & its moon Arca. The Pioneer ships didn't take ALL the citizens of Coral (obviously) and after the second Pioneer declared independance from the planet, it seems everyone gave up on going to Ragol or trying to control it.

Possibly even during Blue Burst era or Episode 3 era of time, the people decided to try to fix the planet. To do so, they created Mother Brain, a powerful AI. She was located on the moon. Since the world was riddled with pollution, war & problems, she worked for a while. Soon Mother Brain decided that the problem of the world was "the population" (Casts, newmen, humans) and genocided pretty much the entire population to 'fix' the planet.

The Great Blank

By nuking everyone back to the stone-age, MotherBrain created the era of "The Great Blank". This is a time when all the technology of Coral was wiped out. She didn't kill everyone though...she kept some Newmen on the moon to try to cultivate a master race. The survivors re-named the planet "Earth & Moon" as the original name "Coral & Arca" were forgotten.

Newmen were likely chosen because they weren't androids who would outsmart their mechanical 'mother' later on, nor were they 'inferior humans' who were 'the cause of' the mess in the first place. They were organic, and you could indoctorinate them as soon as they hatched out of the tubes.

At some point, Motherbrain "perfects" the newmen.
Newmen don't just 'drop dead' (like Sue says in PSO) like they used to. They're stable because she worked on / fixed them.

The plot of 0 starts

Sarissa is sent down by the newmen of the moon, and later Reeve to stop her once she finds out everyone's not a psycho barbarian or whatever lie was perpetuated on the moon. The game's team of heroes goes up to the moon, sets Reeve right, and kills Motherbrain.

With Motherbrain out of the way, it's assumed that the moon-newmen could start sharing some technology/info & help get everyone on the planet out of the stone-age/get Coral fixed back up again.

3010 Circa
3060
3065 Circa
3068
3071 Circa
3076
3077-78
3080 Circa
3081
3082
3083
Mid-3083
3084
3094
3095
3097 Circa
3099
3103-3104
3105
??? After Episode 3