Real World cutoff date

Here is a fun thread for you all. No right or wrong answer, unless 343i really want to answer this. Just made for pure fun and discussion to make you think(being a timeline fan this is always been something that’s interested me)

In the Halo Universe its common knowledge that the Halo Universe uses our past as its Human History. This is made really clear in Halo legends Origins. Where our history is shown before us.
But this begs the question. When does our modern history split from Halos?(aka when do we become a Parallel universe to Halos one)

Now I am here to give a few ideas that could pin point its location. Now no matter what however. Everything up to Macworld in July 21st 1999 is canon. Cause that is before Halo is announced. And nothing is effected by it.(bar Bungie making a game that could change at any point) Thus that is the bare backbone of this.

> Side Note
> Now before I begin how do we explain the “Halo” game dilemma this theory has. Where the existence of the physical Game halo this early in the Halo Universe cant work.
> Sure the games exist as records as proven by this Trailer Linky and also Spartan Assault and Spartan Strike, even Halo Reach.
> But the fact they exist in 20XX in the Halo Universe as video-games cant work. Unless the game Bungie Made wasnt Halo. But a similar game with a fan-base as loyal as us.
> That idea means that sure its a parallel world that splits at July 21st 1999 cause of the fact its not halo but another game that cause a franchise but everything that Happens cultural, world events, and even what we do as fans to this franchise and so on can still happen in the Halo Universe up till 2075 if need be which is the main idea for this thread.(or if humanity speeds up to fast). The only difference is Halo the Video-game isn’t Halo but a different game that cause the same effect as Halo in the Real world.

The easiest one to point out would be the earliest cut off date. The obvious July 21st 1999 when Halo was first announced at Macworld. This makes every event up to July 21st 1999 canon in the Halo Universe(bar the creation of Halo)
And the Halo Universe would then split from our timeline into a world that didn’t get a game like Halo from Bungie.

The latest cut off for our timeline will be in 2021 when the “International Society of Civil Engineers” is created.(Halo 3’s Orbital map says this) unless somehow with really blind luck a “International Society of Civil Engineers” actually does come into existence at that exact time. Or if 343i actually make a website dedicated to it keeping to the illusion of the Halo Universe in the works. Making the cutoff date 2075 when the Unified Earth Government starts up.

But what if I put it to a more recent event. “I Love Bees”. That Website was meant to stick around to the year 2552 so the AI fragments on it can reunite with the Durga half, went off line sometime after October 15 2014. So I can say that is a cut off date also, cause of the implications it causes.

So a recap the dates I said(though you can say your own if you can think up other points these was the first ones that popped into my head)
July 21st 1999 cause of the creation of Halo
October 15th 2014 cause of I Love Bee’s website going offline
2021 cause of the creation of the first major organisation.
Or 2075 cause of the creation of the Unified Earth Government

Now again my question to you all is this. What is the day/year the timelines split too two different paths. And why?