As my old cycle graph post stopped working, I found this one that's even more informative:
I did find bug as of now: if you try to generate graphs for more than one birth dates, the graph will only show the one of the first birth date you entered (unless you close the browser and restart).
What is the 18-day (adept) cycle?
"There is a fourth cycle which we may call the cycle of gateway of magic of the adept or of the spirit. This is a cycle which is completed in approximately eighteen of your diurnal cycles."
" The spiritual or adept’s cycle is an eighteen-day cycle and operates with the qualities of the sine wave. Thus there are a few excellent days on the positive side of the curve, that being the first nine days of the cycle — precisely the fourth, the fifth, and the sixth — when workings are most appropriately undertaken, given that the entity is still without total conscious control of its mind/body/spirit distortion/reality. The most interesting portion of this information, like that of each cycle, is the noting of the critical point wherein passing from the ninth to the tenth and from the eighteenth to the first days the adept will experience some difficulty especially when there is a transition occurring in another cycle at the same time. At the nadir of each cycle the adept will be at its least powerful but will not be open to difficulties in nearly the degree that it experiences at critical times. "