The time difference between F-Zero and F-Zero X is not uniform. Between F-Zero and F-Zero X, the racer Pico goes from 34 years old in F-Zero to 123 years old in F-Zero X, a difference of 89 years. However, Captain Falcon is said to be in his early 30s in the first game F-Zero, while he is stated to be 36 in F-Zero X, giving a maximum amount of time difference to be 6 years.
Contributed by CosmykTheDolfyn