  We calculate the elliptic flow of thermal photons from Au+Au collisions at
RHIC energies for a range of values for the formation time $\tau_0$ but fixed
entropy (or particle rapidity density). The results are found to be quite
sensitive to $\tau_0$. The $v_2$ for photons decreases as $\tau_0$ decreases
and admits a larger contribution from the QGP phase which has a smaller $v_2$.
The elliptic flow coefficient for hadrons, on the other hand, is only
marginally dependent on $\tau_0$.
