A system and method for synchronizing otherwise independent oscillators private to I2C Bus slave devices. An I2C Bus master device can issue two new general call commands, CALIBRATE and ZERO COUNTERS. The I2C Bus slave devices respond to the CALIBRATE command by counting the number of cycles its local, private oscillator makes through during the communication transfer period of the CALIBRATE command on the I2C Bus. All such I2C Bus slave devices measure the same communication transfer period on the I2C Bus, so the differences in the digital measurements obtained by each of them are proportional to their respective oscillator frequencies. The digital measurements are privately used by each I2C Bus slave device to calculate appropriate oscillator prescale factors, and to automatically load the values that will harmonize the final product frequencies of all of the local oscillators on all of the I2C Bus slave devices in the system.