In 1995 at the age of 120 years , she became the subject of her own documentary , 120 Years with Jeanne Calment . On 17 October 1995 Calment reached 120 years and 238 days to become the `` oldest person ever '' according to Guinness , surpassing Shigechiyo Izumi of Japan , whose own claim ( 120 years 237 days old at the time of his death on 21 February 1986 , Calment 's 111th birthday ) has also been subject to considerable doubt .