A wristwatch including a watch case, a bezel mounted to rotate on the watch case, and a dial including at least one luminous index. The luminous index is illuminated through the dial by at least one light source disposed underneath the dial and powered by an electrical energy source. An activation component for activating the light source is housed inside the rotating dial and cooperates with a detection element housed inside the watch case. The activation component, in a determined position of the rotating bezel, detects presence of the activation component by the detection element. The detection element then emits an electrical signal addressed to a microprocessor circuit housed inside the watch case. The microprocessor circuit emits in response to reception of the electrical signal emitted by the detection element an electrical signal that activates lighting of the light source for a determined period of time.