A new technique that allows researchers to determine the amount of time a rock sample has been exposed to daylight could find many applications in geology and archaeology. The new method, pioneered by Sohbati et al., is based on optically stimulated luminescence (OSL) bleaching profiles. OSL is the light emitted on illumination due to the release of stored energy accumulated in crystalline materials through the action of ionizing radiation from natural radioactivity. In solid rock, the latent luminescence has accumulated in response to the amount of natural ionizing radiation absorbed since rock formation. Exposure to daylight removes the acquired latent luminescence in a so‐called bleaching or resetting process. In a rock surface continuously exposed to daylight, this resetting will penetrate deeper into the surface with time (the rock “bleaches”); the longer the rock is exposed, the deeper this bleaching penetrates into the surface. Therefore, measuring the extent of bleaching in a sample can provide a measure of how long the sample has been exposed to daylight.