Convergence SALT2 zero-phase parameter t₀ to the final ‘best’ estimate, $t_0^{\ast }$, as a function of SN phase. We compute the difference in days between the ‘latest’ value of t₀ (the value using the first N detections in g and r) and $t_0^{\ast }$. The horizontal dashed line is where $t_0=t_0^{\ast }$. Points about this line are overestimates of t₀ in comparison to $t_0^{\ast }$. We plot the median $t_0-t_0^{\ast }$ and 68% confidence interval (solid black line and shaded region), estimated in bins of two days, which is the average ZTF cadence.