Temporal reversion, also known as "Return to the past", is one of the greatest and most useful properties of the Supercomputer. It allows the user to return to a point in time of their choosing. Just how far back it can go is unknown, but it seems to be limited to a maximum of roughly two days. In addition, each return trip doubles the processing power of the supercomputer, which in turn doubles X.A.N.A.'s potential power in the first two seasons.
The person at the Factory Interface usually activates a temporal reversion after an attack to erase any damage caused and memory of the events that transpired. The people who have been scanned into the Supercomputer usually remember everything that happened of the previous timeline. However, temporal reversions don't affect events or beings that are linked to Lyoko, undo possession, or deactivate towers. Also, it cannot bring the dead back to life, as pointed out by Odd in Teddygozilla and then later stated by Ulrich in False Start. The two things that remain unknown about this are the reason why and when the Lyoko Warriors first found out about this feature in the program since it was never pointed out by Jeremie when he first discovered the temporal reversion function in X.A.N.A. Awakens. Its power must be based on physical alteration, manipulating every object, force, and living thing in range to a past state, and interfering with people's brains to revert their memories too, but restoring a life that has already died seems beyond its capability.
The return to the past program was used more sparingly after the episode A Great Day, when X.A.N.A. constantly rewinded the same Tuesday over and over to increase his power, leaving the Lyoko Warriors in a pinch. Also, since Aelita was still not fully human at that time, she was still stuck on Lyoko when a return in time was launched.
The characters in the show have used the temporal reversion to their own personal gain. For instance, in The Chips Are Down, Ulrich used it to win the lottery in a misguided attempt to prevent Yumi from moving back to Japan, which got him kicked out of the group temporarily for increasing X.A.N.A.'s strength without permission. Franz Hopper, Aelita's father, used this feature 2546 times over the course of his research, becoming more and more mentally unstable with each return in time.
Temporal reversions can also be very dangerous; in Temptation, Jeremie used it with a headset that multiplied his intellect by 10. Every time he used it, it caused him serious brain damage. The design concept of this headset was created by Franz Hopper. Also, in the episodes The Pretender and The Secret, it is revealed that if Aelita (or anyone else on Lyoko) gets possessed by X.A.N.A. via the Scyphozoa, and a return to the past is launched during the possession, the consequences are unknown, but could be deadly; Aelita would most likely end up under X.A.N.A.'s control for good.
Ever since X.A.N.A.'s escape from the Supercomputer in the episode The Key, it didn't power up with the temporal reversions anymore. Because of this, Jeremie seemed more relaxed about returning to the past even though sometimes it wasn't needed like in the first season.
In Code Lyoko Evolution, it is revealed that Laura modified the boundaries of the temporal reversion program during the episode Virus without Jeremie's knowledge to include herself to be unaffected by the memory loss effect. This seems to be the only alternative to remember events after a return to the past, which doesn't include the subject to be materialized into the Supercomputer. It was also revealed that the event can be specifically altered to erase Lyoko Warriors' memories as well by focusing it solely on the targeted warrior, if they would be too much of a risk for the group. In Mutiny, this was done by Jeremie to Laura, who lost completely every memory she had about the Lyoko Warriors and their fight against X.A.N.A. and Professor Tyron after she launched a preemptive attempt to destroy X.A.N.A. that nearly got William turned into X.A.N.A.'s slave once again.
Times When Used
- New Order
- A Great Day
- Final Mix
- The Chips Are Down
- A Bad Turn
- Attack of the Zombies
- Cold War
- Is Anybody Out There?
- Double Take
- Wreck Room
- Opening Act
- Hot Shower
- The Lake
- A Lack of Goodwill
- Guided Missile
- Canine Conundrum
- Cousins Once Removed
- Music to Soothe the Savage Beast
- Wrong Exposure
- Bad Connection
Season Five: Evolution
Some people are immune to the return trip. This can be achieved by being run by the supercomputer, or being recognized by the supercomputer as someone to not wipe. The following individuals are immune:
|Jeremie Belpois||Gained in X.A.N.A. Awakens.|
|Odd Della Robbia||Gained in X.A.N.A. Awakens.|
|Ulrich Stern||Gained in X.A.N.A. Awakens.|
|Yumi Ishiyama||Gained in X.A.N.A. Awakens.|
|Aelita Schaeffer||Gained sometime in 1994.|
|Waldo Schaeffer||Gained, presumably, on first use.|
|X.A.N.A.||Gained, presumably, on first use.|
|William Dunbar||Gained in Final Round, though pieces of it bled through earlier.|
|William Clone||Assumed, since he was shown remembering behavior from an alternate timeline in A Lack of Goodwill.|
|Monsters||Inherit to the system|
|Laura Gauthier||Gained in Virus, and lost in Mutiny.|