Saturday is a day filled with opportunities to clean up and clear out. So if you are wondering why Hecate is assigned to this day, take another look at what she symbolizes and the magick that is associated with her. That should answer the question.
Hecate was the oldest form of the Greek Triple Goddess, as she presided over heaven, the underworld, and earth. Crossroads where three roads met were especially sacred to Hecate, earning her the title of Hekate of the Three Ways. It’s interesting to note that even after the worship of other goddesses waned, ancient people still worshiped Hecate as the Queen of the Underworld and the Guardian of the Three-Way Crossroad. It was also believed that if you left her an offering of food there, she would grant you her favors. As Hecate Trivia, her triple images were often displayed at these crossroads, where she was petitioned on the full moon for positive magick and on the dark of the moon for cursing and dark magick.
While this last bit of information sounds a little ominous, keep in mind that Hecate/Hekate was known by many titles and is a shapeshifter. Her appearance could and did change often. As a dark moon goddess, her faces are many. To some she may appear as a old crone, hunched over a smoking cauldron and draped in a midnight cape. To others she may appear as a dark beautiful, mysterious, and mature woman wearing a shimmering crown. To some she may be perceived as a maiden priestess. She was called the “most lovely one,” the Great Goddess of Nature, and the Queen of the World of Spirits. This dark goddess knows her way around the earth and the underworld. All the powers of nature, life, and death are at her command.
–Book of Witchery, Spells, Charms & Correspondences for Every Day of the Week