  We show that the transverse momentum dependent elliptic flow $v_2(p_T)$ of
thermal photons is quite sensitive to the initial formation time ($\tau_0$) of
Quark Gluon Plasma (QGP) for semi-central collision of gold nuclei at RHIC
\cite{tau}. A smaller value of the formation time or a larger initial
temperature leads to a significant increase in the thermal photon radiation
from QGP phase, which has a smaller $v_2$. The elliptic flow of thermal photon
is dominated by the contribution from the quark matter at intermediate and high
$p_T$ range and as a result sum $v_2$ decreases with smaller $\tau_0$ for $p_T
\ge 1.5$ GeV. On the other hand we find that the elliptic flow parameter for
hadrons depends only marginally on the value of $\tau_0$.
