Kepler light curves and best-fit models from Quarter 4 (Panel (a)) and Quarter 16 (Panel (b)). Panel (c): the three mid-transit times are well described by a linear model. The uncertainty in the Spitzer transit time (epoch 3) is 23 minutes. Panel (d): posterior probability distributions for the parameters in the linear fit to the mid-transit times (made in-part with corner, Foreman-Mackey 2016).