I guess it would be what is used in quantum mechanics which is the Planck. It is a measurement of distance but also of time. It's about 1.6 x 10^-35 meters or 10^-43 seconds. It's the amount of time that a proton (traveling at the speed of light) takes to travel a distance of 1.6 x 10^-35 meters.

Il papa caca nei legno?