  We consider a non-autonomous Cauchy problem involving linear operators
associated with time-dependent forms $a(t;.,.):V\times V\to {\mathbb{C}}$ where
$V$ and $H$ are Hilbert spaces such that $V$ is continuously embedded in $H$.
We prove $H$-maximal regularity under a new regularity condition on the form
$a$ with respect to time; namely H{\"o}lder continuity with values in an
interpolation space. This result is best suited to treat Robin boundary
conditions. The maximal regularity allows one to use fixed point arguments to
some non linear parabolic problems with Robin boundary conditions.
