System for adjusting an illumination function of a watch

A system for adjusting an illumination function of a watch, the system comprising:

• the watch comprising at least one external timepiece element provided with an autonomous lighting device;
• and
• a portable electronic device provided with a communication unit and a controller configured to control said communication unit,
• wherein the lighting device is formed by an assembly of a plurality of stacked layers connected together and each including one or more of the following functional elements:
• at least one light source capable of generating light in a visible face of a body of said at least one external timepiece element;
• a self-contained power supply unit;
• a communication module;
• and
• a control unit configured to control switching on or off of said at least one light source and to control the communication module,
• said external timepiece element and said portable electronic device being configured to be connected to each other to adjust the illumination of said at least one external timepiece element,
• wherein said assembly comprises:
• a first layer forming a visible face of the external timepiece element comprising said at least one light source of the external timepiece element mounted on the first layer;
• and
• a second layer positioned beneath the first layer and comprising a photovoltaic module of the self-contained power supply unit.