(The following is a work in progress. Feel free to point out new information or errors. I'm figuring all this myself and do not have any reference outside the games themselves. Feel free to add information from things like Ultimania Guides)
(The following is a work of pleasure. I fully understand it impossible to reconcile contradictions that will arise from the iterative process of crafting and expanding these game worlds over many years. Few game scenario writers have the luxery of fully fleshing out intricate histories beforehand, most of this occurs as they go along. I do this for fun.)
(It assumes all anual dates mentioned across games are from the same calendar system. No dates found or mentioned thus far would contradict this assumption up to this point (although things get mucky with the years of Ajoras birth and death). All years listed are in Old Valendian)
Keeping this rather broad for now. I'll do the work of implementing game level details once i'm more confidant in the general flow of major events.
-------------------------------------------------- Ancient Times ----------------------------------
(specific ordering hard to pinpoint in this era)
Giruvegan is built
The Occuria create scions (of darkness?) in opposition to "scions of light". What these scions of light are, who created them, and how this all relates to the Occuria is unclear. A Beastiary entry speaking of the creation of Ivalice talks of war betweens two divine factions. Perhaps there is some truth to the tale.
Ultima leads a rebellion against the Occuria, the Thousand-Years War begins. (origin of Lucavi?) (Zodiark does not partake?).
-1300
Kiltia Church is founded. (as per Magick Pot beastiary entry)
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The Occuria offer Nethicite to the Garif, but they lack the will to "strengthen histories weave".
----------------------------------------------- The Galtean Alliance-----------------------------
Raithwall obtains the Sword of Kings and Nethicite from The Occuria.
-450
Raithwall unites Ivalice under the Galtean Alliance
-400
Roughly 50 years after uniting Ivalice, Raithwall dies
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----------------------------------------------- The 1st Century ---------------------------------- (*1)
0 (or 1)
400 years after Raithwall's death, his last direct descendant passes and the Galtean Alliance is dissolved.
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----------------------------------------------- The 5th Century ---------------------------------- (*2) (FFT History)
Ajora Glabados is born in Bervenia of Lesalia.
Ajora works as a spy against the Yudora Empire. His cover is that of a cult leader, preaching that there is but one true God. (This would assume the current church believes in a pantheon of some measure, which is reinforced by the Kiltia entry in FFXII. This also makes sense, as the Gods worshiped are likely the Occuria which are, of course, a council or "pantheon")
Ajora, fearing death, makes a pact with Ultima. Ultima, known as the High Seraph, had governance over reincarnation...
Ajora is executed as a traitor by the Holy Empire of Yudora. (by Ramza's ancestor if Altimas dying dialogue is to be believed.)
Shortly after Ajora's death, the capital of the Church of Fara, Murond, sinks into the sea and Ajora's death becomes associated with this phenominon. His cult cover takes on a life of it's own and Ajora becomes known as St. Ajora, a "child of god" (a christ figure).
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700 - During a trip to the Jagd Difohr, Cid meets Venat for the first time (presumably in or near Giruvegan). Archadian research into Nethicite begins.
----------------------------------------------- The 8th Century ---------------------------------- (FF XII)
701
Plague inflicts the city of Rabanastre and kills Vaan and Rek's parents.
704
Archadia begins it's invasion of the Galtaen Peninsula. The official "excuse" is fear of increased Rozarrian prescence at the Nabradian border. The real reason (Vayne's real reason) is to obtain the deifacted Nethicite.
Nabudis is destroyed by the Mid Light Shard.
Nalbina and Rabanastre fall under Imperial Control.
706
The events of Final Fantasy XII proper.
The Sun Cryst is destroyed. (thus ended the Age of Stones)
Ondore publishes his memoirs.
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A great cataclysm (or at least an interesting turn or series of events) leads to a downgrading of technology.
----------------------------------------------- The 17th Century ---------------------------------- (*3) (FFT)
Outbreak of the Fifty Year War
50 years later - Fifty Year War ends and King Omdolia Atkashca obtains the throne from King Denamunda.
One year after end of 50 year war King Atkashca dies. His son, Orinas, is only 2. Desire for control over Ivalice spurns the Lion War.
Three major figures involved in the Lion War are killed. Larg by Dycedarg, Goltana by Delita, and Funeral by Vormav. The Lion War essentially has ended and Delita has positioned himself to be the new King.
Ajora's pact with Ultima comes to fruition. Ajora is reincarnated, but is possessed by Ultima. Together they are Altima.
Ramza defeats Altima in the depths of Murond Death City. "You...you're the descendant of the one who killed me before!"
Delita becomes King.
Durai Report is written by Olan Durai.
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Durai Report is published by Alazlam Durai.
---------------------------------- Difficult to place in the Time Line ------------------------
The events of Vagrant Story
Vagrant story has more in common with FFT than FFXII in terms of setting and feel of world. This, functionally, was a result of the fact that FFT and VS were developed at more similar times than FF XII. Indeed, the Ivalice of FFT and VS feels quite a bit different than the Ivalice of FFXII in terms of races, levels of technology, and just the overall feel of the time periods. Whether this means they take PLACE in the same time is debatable.
There are few hard numbers to work with, but one stands out. 2,000 years old. Lea Monde is 2,000 years old. That alone tends to put the game in a later time frame. In spirit of centering dates on 0 (or 1), Placing it 300 years after FFT doesn't feel like a stretch and would make it's founding the time of the fall of House Galtea. So until further information is given, that's where I'm sticking it

.
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(*1) - Took a bit of logic to get here. Clearly something important happens in the year 0 (or 1) to base a calendar around that date. As per the FFXII beastiary you can figure that Direct House Dalmasca control over Dalmasca began 700 years previous and was synonymous with the fall of house Galtea. It makes sense to assume this occured in 0 (or 1) and is the "important event". All further negative dates are figures drawn from numbers you can find in the FFXII beastiary
(*2) - As per the bio of Alazlam in Final Fantasy Tactics. "His writings include 'The Mysteries of the Lion War', 'The Real Image of the Holy Ajora', and 'Durai Writings: The Truth of the 400th Year". Whether the truth of the 400th year refers to the period of time of Ajora or the Lion War is ambiguous, however assuming it refers to Ajora's period falls in line with everything else. If we assume the 400th year refers to the period of the Lion War (and we assume the 400th year is as per the Old Valendian calendar) that would make FFT occur before FXII, which makes less sense given the asserted extinction of moogles, talk of ancient airship technology, and other factors.)
(*3) - According to Ajoras bio in Final Fantasy Tactics, he was born 12 centuries before the events in Final Fantasy Tactics. While there is enough room for error at this point to give or take a century, I'm going with the most literal interpretation. (400 + 1200 = 1600)
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Unresolved issues
1 - The church. The Church of Fara, The Light of Kiltia, The Murond Glabados Church. Are these the same churches with name changes over time? I'm inclined to think so. We see a connection between Fara and Kilitia in the prayer utterance of Faram and in their belief in a dualism pantheon of deities. Beastiary entries about Kilitia then connect it to Ajora, who is obviously associated with The Murond Glabados Church. An issue occurs when the date of the crossover to the name of Muron Glabados Church. One would assume this change would happen within a reasonable time frame after the death of St. Ajora, however it was called Fara during Ajora's lifetime, and Kiltia 300 years later. When did it become known as Glabados? According to the above timeline the name change would have had to have happened at least 400 years after Ajora's Death. It is also possible that These churches are actually seperate, but similar, IE: like protestant faiths.
2 - The Zodiac Stones. Who? What? When? Where? Why? How? Likely some form of Magicite, at least.
3 - Ajora and the Kiltias church. As per the Magic Pot entry in FFXII, Ajora was born shortly after the founding of Kiltia ("several years"). This same entry suggests that this would have occured about 1000 years BEFORE the formation of the Galtean Alliance. However the Alazlam entry in FFT suggest Ajora was born in the 4th century (if we assume FFT happens after FFXII). Which is nearly 800 years AFTER the formation of the Galtean Alliance. Ruh Roh Reorge. Either we have a contradiction, a difference in calendars, or a mis-translation (or more than one Ajora). The founding of Kiltias is QUITE a bit of time before anything else happens, there's a long span of time there we might place FFT, but we have to ignore a few assertions about FFT, such as moogles being extinct. There's also the issue that Ajora was executed by the Church of Fara, not Kiltia.
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