I've made an attempt at some alt-history in trying to construct a timeline for the original timeline. Here goes:
13 May 1965
Sarah Connor Born (Approximate, based on her being 19 in Terminator 1)
12 November 1982
Yuri Andropov becomes General Secretary of the Soviet Union.
8 May 1984
Sarah Connor sleeps with the man who left a voicemail on her phone in the original T1 (Approximate). This man is the true biological father of John Connor in all timelines. In all timelines, she never really knows her son's true biological father. In later, altered timelines; Kyle Reese becomes John's "spiritual father".
Late 1984
Greg Simmons and Jack Kroll leave Cyber Research Systems (CRS) to found Cyberdyne Corporation. In the Novelization of T1, they're the ones who discover the arm and skull in the factory and hide it from their superiors and found Cyberdyne.
12 February 1985
John Connor born. (Approximate)
Circa 1986
Cyberdyne wins contract to supply Advanced Tactical Fighter (ATF) chip subsystems to Northrop.
Late 1987
Miles Bennet Dyson joins Cyberdyne as an engineer on the ATF chip systems.
January 1989
Richard Lugar inaugurated as 41st President. (EDIT: Anyone but HW Bush, because we need to push "Star Wars" all the way to the end, and even with the USSR hanging around post 1992...we need more impetus).
23 April 1991
Northrop-McDonnell Douglas YF-23 announced as winner of ATF Competition.
Mid 1992
Cyberdyne wins contract to supply computer systems for the Strategic Defense Initiative Organization ("Star Wars") Strategic Defense System; which implements ground based and space based defensive and offensive systems. Design of the 4000 series begins.
Late 1992
Miles Bennet Dyson appointed Director of Special Projects to oversee the design of the 4000 series distributed supercomputer.
26 May 1993
Yuri Andropov dies.
9 June 1993
KGB Chairman Vladimir Kryuchkov becomes General Secretary of the Soviet Union.
Circa 1994
Cheyenne Mountain Complex selected as the ground-based command and control node for the SDIO Strategic Defense System.
Early 1995
Construction begins on enlargement of Cheyenne Mountain Complex, effectively tripling it's size to support the SDIO Strategic Defense System.
Cyberdyne has become the largest supplier of computer components to the US Defense Department due to it's F-23 and SDS Contracts.
Late 1995
First Orbital Weapons Station launched into geosynchronous orbit via National Launch System (
https://en.wikipedia.org/wiki/National_Launch_System).
Circa 1997
Cheyenne Mountain Complex enlargement completed. Installation of the Cyberdyne 4800C System begins.
Late 1997
SDIO: Strategic Defense System renamed "SKYNET".
Early 1998
24th and Final Orbital Weapons Satellite launched into orbit. SKYNET Orbital Construction Complete.
8 June 1999
SKYNET Ground Based Construction complete with installation of last cabling in Cheyenne Mountain Complex Expansion.
4 August 1999
SKYNET Activated.
Late August 1999
John and Sarah Connor go on vacation to Argentina to visit friends. John is fourteen and a half years old.
29 August 1999
SKYNET Becomes Self Aware at 2:14 AM EDT.
SKYNET launches the weapons under its control at 2:43 AM EDT. (JUDGMENT DAY)
18 July 2003
Kyle Reese Born (Approximate, based on his age being 26 in Terminator 1)
2021
Kyle Reese Assigned to 132d under Perry
2025-2026
SKYNET deploys first experimental prototype T-800 Infiltrators in limited field tests.
2027
Kyle Reese Assigned to Recon/Security under John Connor following the conclusion of the Oregon and New Mexico Offensives.
SKYNET standardizes the T-800 Infiltrator as Standard Issue.
11 July 2029
Terminator 1/2 Future War Finale. John Connor is 45 years old.
OUT OF CONTEXT NOTES:
12 May 1984
Beginning of T1 (Events have not occurred in this timeline)
14 May 1984
End of T1 (Events have not occurred in this timeline)
Circa 1995
Events of T2 (Has Not Occurred in This Timeline)
Circa Sep 1999
On a "Tuesday in September '99" is how John Connor recalls Judgment Day as occurring in the Future War scenes in the original T2 script draft.
T-800 Introduction Notes:
Reese in T1 refers to the T800 Infiltrators as "New", plus he says they can't be made "not for about forty years." This places their introduction to somewhere between 2024 and 2029.