Method of adjusting the operating frequency of an electronic watch by means of a computer application installed in a portable electronic device including, in particular, a microcontroller, a light source and a screen, wherein the electronic watch comprises an electronic module including: - an oscillator and a frequency divider circuit which is arranged downstream of the oscillator and which is configured to transmit a pulsed signal corresponding to the operating frequency - an operating frequency adjustment circuit including a memory storing an inhibition value, the adjustment circuit being arranged to inhibit one or more pulses transmitted by the frequency divider circuit as a function of the inhibition value - a communication unit for communicating with the portable electronic device, the communication unit comprising an optical sensor arranged to receive a signal in the form of a sequence of optical pulses, called a modulated optical signal - a microcontroller arranged to control the operating frequency adjustment circuit as a function of the modulated optical signal received by the communication unit, the adjustment method including the following steps, performed by the computer application: - generating a pulsed reference signal in the portable electronic device - converting the pulsed reference signal into a modulated optical signal consisting of light pulses - transmitting to the optical sensor of the communication unit of the electronic watch the modulated optical signal via the light source or via a modulation of the light emitted by the screen of the portable electronic device, and the following steps, performed by the microcontroller of the electronic watch: - reconstituting the pulsed reference signal from the modulated optical signal received by the optical sensor - correcting the inhibition value stored in the memory of the adjustment circuit as a function of the pulsed reference signal. - an oscillator and a frequency divider circuit which is arranged downstream of the oscillator and which is configured to transmit a pulsed signal corresponding to the operating frequency - an operating frequency adjustment circuit including a memory storing an inhibition value, the adjustment circuit being arranged to inhibit one or more pulses transmitted by the frequency divider circuit as a function of the inhibition value - a communication unit for communicating with the portable electronic device, the communication unit comprising an optical sensor arranged to receive a signal in the form of a sequence of optical pulses, called a modulated optical signal - a microcontroller arranged to control the operating frequency adjustment circuit as a function of the modulated optical signal received by the communication unit, - generating a pulsed reference signal in the portable electronic device - converting the pulsed reference signal into a modulated optical signal consisting of light pulses - transmitting to the optical sensor of the communication unit of the electronic watch the modulated optical signal via the light source or via a modulation of the light emitted by the screen of the portable electronic device, - reconstituting the pulsed reference signal from the modulated optical signal received by the optical sensor - correcting the inhibition value stored in the memory of the adjustment circuit as a function of the pulsed reference signal.