  We prove a Fredholm determinant and short-distance series representation of
the Painlev\'e V tau function $\tau(t)$ associated to generic monodromy data.
Using a relation of $\tau(t)$ to two different types of irregular $c=1$
Virasoro conformal blocks and the confluence from Painlev\'e VI equation,
connection formulas between the parameters of asymptotic expansions at $0$ and
$i\infty$ are conjectured. Explicit evaluations of the connection constants
relating the tau function asymptotics as $t\to 0,+\infty,i\infty$ are obtained.
We also show that irregular conformal blocks of rank 1, for arbitrary central
charge, are obtained as confluent limits of the regular conformal blocks.
