Friday carries Venus's significations: love, beauty, pleasure, harmony and the cultivation of relationships, following the qualities classical astrology assigns the planet nearest the Sun after Mercury and, alongside Jupiter, one of the two classical benefics. Older astrological and magical handbooks recommend Friday for matters of romance, artistic work, social gatherings and anything meant to build goodwill or attraction between people.
Friday's reputation varies more by culture than most of the week: in some folk traditions it carries an ill omened association, particularly when it falls on the thirteenth of the month or coincides with religious observances of a solemn character, while in astrological practice proper it retains Venus's generally favourable and sociable reputation without that specific superstition attached. The two readings, folk caution around the calendar date and astrological confidence in the planetary day, coexist in the wider culture without either displacing the other.
Sources A History of Western AstrologyNicholas Campion with Grimoires: A History of Magic BooksOwen Davies