Goetia In Theory & Practice
I try to ensure that my evocation is COMPLETED by the time of the Full Moon -- The day of a full moon occurs on the 14th Lunar Day. However, it really depends on the spirit you're evoking.
Say, if the Full Moon occurs at 9:00 pm, you'll need to evoke a spirit that is able to be evoked at that time -- which, will cancel out any of the Dukes (ruled by Venus), as they can only be successfully evoked from 6am until Noon.
I'm writing a book right now that I think will revolutionize the way Magicians perform evocations. It really is all about the timing.