In 2379, when she was exposed to the biotemporal field of the bio-temporal chamber created by The Doctor in an attempt to extend her lifespan, Kes's cells were put into a state of biotemporal flux due the reactivation of dormant chroniton particles in her cells, causing her to experience a series of backward time jumps, essentially living her life in reverse. When Kes arrived in 2373 of an alternate timeline, and explained what was happening to the crew of Voyager, The Doctor used a bio-temporal chamber to expose Kes to a precisely modulated field of antichronitons in an attempt to purge her system of the chronitons, and bring her back into temporal sync with the rest of the crew. When Kes was exposed to the antichronitons, she experienced a series of jumps, all the way back to her concept