Different dates, times, planets and moon phases may benefit in the casting of different types of spells or rituals. It is possible to "fine tune" the timing of witchcraft by choosing a date and time when the season, astrological configurations, day of the week and phase of the moon are all favorable to the spell you wish to cast.
It is also essential to trust your intuition. Do not cast a spell if you feel that the timing is incorrect, as the power of the ritual will be lessened.
A list of astrological bodies and their various day correspondences are listed with types of spell work they are beneficial to follows:
The sun - Sunday. Beneficial to spells aimed at gaining money, finding treasure, harmony, friendship and fortune.
The moon - Monday. Beneficial to necromancy spells, traveling over water, visions and love operations.
Mars - Tuesday. Beneficial towards spells concerning death, destruction, hatred, discord and channeling spirits.
Mercury - Wednesday. Beneficial towards workings concerning commerce, obtaining knowledge, theft, deceit or fear.
Jupiter - Thursday. Beneficial towards spells concerning money, status and good health.
Venus - Friday. Beneficial to ceremonies of lust, love, pleasure or friendships.
Saturn - Saturday. Beneficial towards workings that concern injury, death or destruction.
(Reproduced from: http://astrologicaltiming.blogspot.co.uk/2012_06_01_archive.html)