Events changed by the arrival of the reprogrammed T‑800
Notes on Chronology 5
When Judgment Day happens, John is probably not prepared for it. He believes they prevented Judgment Day. He may be haunted by a feeling, but he doesn't necessarily prepare and certainly not for 2004.
John realizes several things at this point. Kyle told Sarah that Judgment Day was going to happen in 1997. Given what Myles Dyson told John about the progress of Cyberdyne's development, the 1997 date makes sense. However, by destroying Cyberdyne they prevented the 1997 date. Yet Judgment Day happened anyway. What Kyle told Sarah and what actually happened do not match.
John knows that the only reason they were able to destroy Cyberdyne was because of the reprogrammed T‑800, without its information and help they probably would have failed. John also knows that he reprogrammed the T‑800 and sent it back. Once Judgment Day happens in 2004, John must understand that his actions in the future caused Cyberdyne to be destroyed and radically changed the past.
Because Judgment Day happened regardless of the destruction of Cyberdyne, John decides that he is no longer going to attempt major changes to the past as he has no confidence that his actions won't make things worse, and there appears to be a certain inevitability to the events he is attempting to prevent.
John then makes the decision that he is simply going to ensure that what has already happened happens again, and the only alterations will be to give Sarah, himself and the resistance the best chance of survival and success.
He will send Kyle back. However, he realizes that Kyle will have the 2004 date for Judgment Day and, in John's past, Kyle told Sarah it would be 1997. Also, Kyle had told Sarah that Cyberdyne was the company that built Skynet, but John knows that CRS did this.
Therefore he decides that he will have Kyle lie to Sarah. He does this for two reasons. The main reason is to not change what has already occurred, to leave the past as untouched as possible. The second reason is that, if Sarah thinks Judgment Day occurs in 2004, she will not be as prepared as she otherwise would be.
Next, in order to postpone Judgment Day from 1997 to 2004 he decides to reprogram the T‑800 with the information it will need to destroy Cyberdyne. If he has slipped up and missed something and Judgment Day occurs in 1997, Sarah and he will be prepared. If he did not miss anything and the past remains unchanged, Judgment Day will occur in 2004.
He was not prepared for the 2004 date so, in order to better prepare himself yet not alter the past if possible, he decides to have the reprogrammed T‑800 make no mention of the 2004 date. Rather, he will reprogram another T‑800 and send it back to 2004 to get he and Kate to a safe location.
In the section on Judgement Day, where we make a case that it took place in 1994, we partly rely on statements made by the T‑800 as to dates and here we make the claim that this T‑800 was reprogrammed by John to give false information. However, the information we used was the T‑800's claim that in 3 years it would be 1997 and in 35 years it would 2029. There are good reasons for John to have it lie about Cyberdyne / CRS and to lie about Judgement Day happening in 1997 instead of 2004, but there is no reason to have it claim that 1997 is 3 years in the future and 2029 is 35 years in the future unless this were true. If the year it claimed these was not 1994, no one would believe it.
We do not know for certain whether Skynet has sent back a T‑X or not. The T‑X is an anti-Terminator Terminator, although not exclusively. Skynet does not know that the T‑800 has been sent back to help Kate and John as that event had not occurred yet, however, it may know that a T‑800 was sent back to 1994 and so decides to send a T‑X in case the resistance is able to send a T‑800 to 2004. After all, in Rise of the Machines the T‑800 says "My presence in this timeline has been anticipated."
In conclusion, in order for the past to remain as unchanged as possible, John must convince Kyle to lie to Sarah. Kyle will tell her that Judgment Day happens in 1997, he will tell her Cyberdyne built Skynet, he will not tell her about the 2004 date, he will not tell her about the 1994 Terminator. Additionally, John reprograms the T‑800 he sends to 1994 to withhold certain information. It too will say that Cyberdyne develops Skynet and it will make no mention of the 2004 date.