#[My math may be a little off but I can't really take into consideration D.O.B or D.O.D since we don't know exact dates for Ifalna]

[caeca-iustitia]

One thing I don't quite understand is this:

Vincent was born on October 13th 1950.

In 1977 Vincent would be 27, which is their canonical age of death.

So why is, based on what I've seen, the year of their death listed as 1984? 

That would make them 34, not 27.

And I know that the different sources say 'between 20-30 years ago' and '23 years prior to the events of FFVII' but still.

Sephiroth is "killed" in October 0002 (or therein about) whilst his age is noted as somewhere between 25-30.

[ If we say that the 30-year estimate is correct then Sepiroth would have been born in 1977 (this is based on the start date of FFVII being December of 0007 and thusly 5 years after Sephiroth fell into the Lifestream following Cloud injuring him).

Come 0007, Sephiroth would be 30 but in 0002- when he died- he was probably 24 based on the fact that the 'Nibelheim Incident' happened in October. 

This puts into question whether Sephiroth was born before Vincent was shot by Hojo or afterwards. 

It isn't explicitly stated that he had been born by the time that happened, only that Lucrecia was very sick due to the Jenova Cells. I choose to interpret it as him being born, Vincent confronting Hojo after a few weeks to make sure Lucrecia is okay then Hojo shooting them to experiment on them. However, a case can be made that Lucrecia was heavily pregnant at the time and Vincent confronted Hojo before Sephiroth's birth.

Either way, Vincent was likely dead by the end of 1977 based on this theory. ]

[ If we assume that Sephiroth is, instead, 25 then this throws everything I thought I knew into question.

Firstly, Sephiroth would have been born in 1982 and would have been 20 when he fell into the Lifestream and "died". He would be 25 by the time FFVII begins. 

Secondly, this likely makes Vincent 31 or 32 when they "die" not 27 or 34 since we know that Lucrecia was either pregnant with Sephiroth or had just given birth to him (see my last theory on this).

Thirdly, this means that Vincent's sleep would not have been 30 years- as has been pretty well established to have been the case for who knows how long- as they wouldn't have been in the coffin long enough for that to be the case. It would likely have been closer to about 23-25 years rather than the 28-30 we are used to hearing about.

Lastly, Sephiroth is presumed to have been a member of SOLDIER since he was around 20. How old does this make him during Crisis Core or First SOLDIER then? Surely he'd be around 18 or so then, yes? This opens up so many more questions than it answers. ]

TL;DR - I have no idea what to do since I've always had Vincent "die" at 27 but if the timeline is this confused then God only knows how confusing the rest of it is based on all this information being incorrect or inaccurate.

Also... What idiot looked at 1984 and said "Ah, yes, this character that was born in 1950 would be 27 right now..."?