I'm sorry if I'm being na?ve for saying this, but, Lance, if you want to find out more about this topic, wouldn't it help if you raised the issue to Ken Williams himself? Or to programmer Jeff Stephenson? Or maybe Al Lowe, who seems to be more chatty and approachable? I'm asking from complete ignorance. I don't know if you've already tried to contact them about this subject.
@pabuslem: The thing is, when we're dealing with the earliest part of the timeline, people don't remember! That the earliest language was called GAL (not AGI), that Arthur Abraham was the lead creator of GAL, and so on. These are things that we (i.e. Lance) have had to dig up ourselves, because the Sierra alumni have forgotten.
@pabuslem, I have spoken to Jeff and Al multiple times over the past 15 years or so, and Collector is right, they don't remember specific details, such as dates. 40+ years ago is indeed a long time. They remember the big events but not exactly when they happened. Jeff wasn't one of those that was laid off mid-1984 (I think Jeff and Bob were two of the only programmers that were not laid off), but Al was laid off, but was hired back almost immediately as a contractor working on the Disney projects, across several of those Disney games. He remembers that kind of detail but not exactly when that happened. They usually remember the relative order of when things happened though.
I haven't spoken to Ken in the past, other than swapping a few comments in places like youtube. I know that I could easily do so, but I would probably prepare a set of questions that I think he would be more likely to remember. Ken admits himself (as he mentions in his recent book) that he can't remember the details, and that what he covers in his book is not guaranteed to be accurate (not sure he uses exactly those words, but words to that effect). I've also seen a number of video interviews with him where he mentions he struggles to remember the details. I am currently thinking that I will probably send the timeline to him when I have it ready.
My approach is to try to find as many dates that can't be disputed, things that can be set in stone. For example, I know that one of the programmers that worked on one of the Disney contracts in 1984 signed the contract on the 17th July 1984. I also know that Sierra and Disney announced their partnership and initial line up Disney educational games at the start of June 1984 (at the Summer CES show that year). I also know that a newspaper article from the Sierra Star dated 28th June 1984 mentions the same Disney/Sierra partnership, mentions the change in name from Sierra On-Line to simply Sierra, and mentions that the new building is still under construction. I found another article from towards the end of 1984 that states that Sierra got another $2 million in venture capital in July that year, i.e. July 1984.
These are the kinds of dates that everything else can be slotted between. If we know that some events happened after or before one of these fixed points in time, then we can narrow in more on a rough date.
Dates like the timestamps on original game disks, or like in this big source code archive, are also indisputable. I've been looking at the file timestamps from 1986 in the Donald Duck's Playground game in that archive. It is clear from that that Al was working on the first AGI version of that game in early 1986. Dev work began at the end of February 1986, the majority of the work happened in March 1986, with a bit more in April/May, finally finishing early June 1986. The AGI documentation in the DOCO folder have timestamps dated 29th May 1986. This happens to be just before the timestamp usually associated with AGI v2.001 (9th June 1986), which was the first AGI V2 interpreter version we know of, that was used in that first AGI version of Donald Duck's Playground. That all ties up then. Al was working on converting the original Donald Duck game (which came out on the C64 at the end of 1984) to AGI v2 over that first half of 1986. Jeff was most likely providing him with early cuts of the AGI v2 interpreter, with 2.001 being what ended up in the release.