The Berkeley algorithm is a method of clock synchronisation in distributed computing which assumes no machine has an accurate time source.
Generally speaking, the algorithm is: With this method the average cancels out individual clock's tendencies to drift.
Gusella and Zatti released results involving 15 computers whose clocks were synchronised to within about 20-25 milliseconds using their protocol.
Doing so would break the property of monotonic time, which is a fundamental assumption in certain algorithms in the system itself or in programs such as make.
This prevents the overall system time from being drastically skewed due to one erroneous clock.