MICHAEL'S THEORY:
We are presented, in-game, with a very exact date for Phantasy Star I: Space Century 342. Likewise, Phantasy Star IV presents us with an exact date, as well: AW 2284. But when it comes to the dating of Phantasy Star II, things become a little more complex.
Numerous references within the games allow us to place PSII at approximately 1000 years after PSI, and approximately 1000 years before PSIV. Further, there is one reference within PSIV that, on the surface, would seem to provide us with an exact date for PSII. Upon reaching the wreckage of the world ship which crashed to Motavia six months previously, Rika says, "Parma, the first planet of the Algo solar system, was destroyed in AW 1284 when the artificial satellite, Gaira, crashed into it..."
This would seem to indicate a gap of exactly 1000 years between PSII and PSIV. However, three facts from the games have convinced me that the exact date of PSII is AW 1286, not AW 1284.
Fact One: The Dimensional Seal:
Le Roof's dialog in PSIV explains the concept of the dimensional seal that holds The Profound Darkness within its prison: "...there were fluctuations in the strength of the seal. Once every thousand years, its power would weaken drastically." In other dialog, Le Roof establishes that "the seal" is "a gigantic seal of three planets on one fixed star..." If fluctuations in the strength of the seal cause its power to weaken drastically every one thousand years, then shouldn't the complete loss of the planet Palma in PSII affect the seal's strength even more drastically? If the seal, when completely normal (meaning, when the star Algo and all three planets are intact), fluctuates in strength every 1000 years, shouldn't the loss of such a significant portion of the seal cause its fluctuation to be much greater -- or more precisely, much sooner? A gap between PSII and PSIV shorter than 1000 years thus seems appropriate and logical.
Fact Two: Wren's Age:
At the time of PSIV, Wren is 998 years old. PSIV also establishes that the loss of Mother Brain and the subsequent collision of a fragment of the exploding planet Palma into Motavia brought about a massive loss of technology known as The Great Collapse. While I certainly believe some technology survived and was restored on Motavia during the gap between the loss of Mother Brain and the impact of the fragment of Palma -- and while I believe the Palman culture on Motavia would indeed have been capable of making Wren-type androids during this period -- it seems to me it would have been a waste of time, effort, and precious materials. Further, note that the only other place in the series where we encounter Wren-types (not 'ren-types but Wren-types) is the Alisa III -- evidence that it is possible that the only place Wren-types existed in Algo was Palma. Add it all up, and the only idea that makes sense to me is that Wren was created prior to Mother Brain's destruction, which, based on his age of 998, would place PSII at 998 years before PSIV, at a date of AW 1286.
Fact Three: The Biosystems Lab Data Recorder:
When the Central Tower Librarian presents Rolf and his friends with the analysis on the Biosystems Lab data recorder, she says, "Please look at this graph. It shows the amount of energy consumed in the last couple of years."
Knowing that the graph contains data for "the last couple of years," and seeing that it contains data for the year AW 1285, PSII's date would clearly appear to be something later than AW 1285 -- such as my suggested date of AW 1286.