Markov chain Monte Carlo power-law model fit to ZTF g and r-band fluxes to estimate the time of first light t_first. The fitting is limited to the first 12 days after t_first, during which the light curve clearly follows a power-law rise. Power-law model fits are performed separately on the ZTF g- and r-band light curves to determine t_first and α independently for each band. In the top panel, the g- and r-band fluxes are shown with arbitrary and distinct scales for visual clarity. The inferred (weighted mean) t_first is shown by a vertical dashed line, with the shaded region indicating the uncertainty limits. In the bottom panels, the vertical and horizontal lines indicate the t_first and α values, as inferred from each MCMC fit.