Planck time
The Planck time is the length of time at which no smaller meaningful length can be validly measured due to the indeterminacy expressed in Werner Heisenberg's uncertainty principle. Theoretically, this is the shortest time measurement that is possible. Planck time is roughly 10−43 seconds. However, to date, the smallest time interval that was measured was 10−21 seconds, a "zeptosecond."