Planetary hours have been mostly seen as a restriction in modern magic rather than a tool which can focus and strengthen a ritual. It is said that you should not do a ritual if you are going to end up doing it on the wrong day. The best time to do a Saturn ritual would be the hour of Saturn on Saturday. However this is a simplistic and inflexible approach. What you need to work out is what your ritual is really doing and what planetary powers are involved.   So for example you might what to do a binding spell to prevent someone taking a certain course of action.  Logically Saturday would be a great day for a binding spell.  But would we