Error analysis of the time delay measurement based on delay estimations on simulated light curves that mimic the light curves displayed in Fig. 1. The horizontal axis corresponds to the value of the true time delay used in these simulated light curves. The gray colored rods and 1σ error bars show the systematic biases and random errors, respectively. Our measured time delay of Δt = −20.5 ± 1.0 days is discrepant with the true time delay of 22.75 days listed in the TDC1 truth files at the level of 2.25σ. The difference in sign of time delay is simply a matter of convention.