We know that the stability of Hamiltonian systems is at most neutral and so it can be violated by some non-Hamiltonian perturbation. However, if we confine ourselves to the space of Hamiltonian systems, then the notion of strong stability is meaningful. The stability of a linear Hamiltonian system is strong if it is preserved by any small deformation of the Hamiltonian.
In the Time-Invariant case, the (strong) stability of the Hamiltonian system is implied by the strong stability of its linearization. On the other hand, a linear periodically time-varying Hamiltonian system is equivalent to some linear time-invariant Hamiltonian system, by a linear time-varying transformation. Can we construct a local periodically time-varying nonlinear transformation to obtain a time-invariant Hamiltonian system from the periodically time-varying one? If so, similar to the time-invariant case, we can conclude stability properties of the periodically time-varying Hamiltonian system from its linearization.
I have not found an (explicit) theorem on it, in the well-known references.