Because the number three is considered to be the most magickal of all numbers, and this is the third day of the third month, it is believed that this is the most favorable time for Witches and practioners of Magicks to work all of their practices.
This day is sacred to all Triple Goddesses and Lunar Deities. The magickal properties of pyramids is also said to be at its peak on this day because of the actual form of a pyramid having three sides.