We consider autonomous and non-autonomous evolution equations on a time interval \([0,\tau ]\) in a Banach space X with the nonstandard time–boundary condition \(u(0)=\Phi u(\tau )\) , where \(\Phi \) is a linear map on X. If \(\Phi =0\) , this is an initial value problem, whereas \(\Phi =I\) corresponds to periodic boundary conditions, and \(\Phi =-I\) to antiperiodic boundary conditions. Our main point is to establish maximal \(L^p\) -regularity. In the non-autonomous case we consider two situations. The first concerns time-dependent operators with a fixed domain. In the second one we take \(X=H\) a Hilbert space and consider evolution equations associated with non-autonomous forms. Of special interest is then maximal regularity in H with a nonstandard time–boundary condition.