Ahhh my favorite number. Cloaked in mystery and for a reason. It is the number of the completion of a cycle, the cleansing and purification as something dies and is reborn.
“Having left the tree from where he hung, the Fool moves carefully through a fallow field, head still clearing from visions. The air is cold and wintry, the trees bare. Before him, he sees, rising with the sun, a skeleton in black armor mounted on a white horse. He recognizes it as Death. As it stops before him, he humbly asks, “Have I died?” He feels, in fact, rather empty and desolate. And the Skeleton answers, “Yes, in a way. You sacrificed your old world, your old self. Both are gone, dead.” The Fool reflects on that, “How sad.” Death acknowledges this with a nod. “Yes, but it is the only way to be reborn. A new Sun is rising, and it is, for you, a time of great transformation.” As Death rides away, the Fool can feel the truth in those words. He, too, feels like a skeleton, all that he was stripped away. This, he understands, is how all great transformations start, by stripping things to the bone, and building fresh upon the bare foundations.”
Perhaps the stigma associated with the number 13 stems from the suppression of the of the sacred feminine by the power hungry patriarchal church as there are thirteen moons in a year, the moon being a reflection of the female cycles and the Earth. The Gregorian calendar is mechanical and divorced from True Nature, the real calendar has thirteen months.