Left: Dark Energy Survey (DES) g-band image of the lens system DESJ0501-4118. Middle: GaiaG-band light curves of image 1 (black dots) and image 2 (magenta dots); the empty circles represent the image 1 light curve shifted in time by 121 days and in brightness by 0.21 mag to match the behaviour of image 2. Dotted lines are cubic spline interpolations through the 30-day binned light curves. Right: DCF between the image 1 and image 2 light curves (black diamonds) and between their splines (grey dots); they indicate a time delay of ∼120 days of the flux variations of image 2 with respect to those of image 1. The inset shows the result of 3000 Monte Carlo DCF simulations; the yellow strip highlights the interval of the time-lag centroid values including 68% of cases (1σ).