In magick, the timing of a ritual or the summoning of spirits can be an important factor in determining its success. The best day to summon a spirit depends on the specific spirit and the purpose of the ritual.
Some spiritualist writers suggest that the best day to summon a spirit is on a day that is associated with the spirit's specific energies or powers. For example, if the spirit is associated with wealth or prosperity, it may be best to summon it on a Thursday, which is associated with the planet Jupiter, which is associated with wealth and abundance.
Others suggest that the best day to summon a spirit is on a day that is associated with the purpose of the ritual. For example, if the ritual is for protection, it may be best to summon the spirit on a Tuesday, which is associated with the planet Mars and the element of fire, which is associated with protection and strength.
Some spiritualist writers also suggest that the best day to summon a spirit is on a day that is associated with the element that the spirit is associated with. For example, if the spirit is associated with the element of water, it may be best to summon it on a Monday, which is associated with the Moon, which is associated with the element of water.
It's also important to note that the best day to summon a spirit can also depend on the tradition and the personal preference of the magician. Other writers suggest that the best day to summon a spirit is on a day that is considered to be favorable for the magician or that aligns with their personal spiritual practice.
In general, it's recommended to research the spirit you're trying to summon and consult different grimoires and sources to find the best day. It's also essential to have a good knowledge of astrology, numerology and the correspondences of the days, planets and elements when it comes to evoke a spirit.
It's also important to remember that the most important thing is to have a clear intention, good protection and to follow proper evocation techniques, the day is not the most important factor, but rather the preparation, focus and the will of the magician.