friday or sunday [i also heard monday, but that was only once so i don't know]
so on friday it should be cast at 8am, 3pm or 10pm. on sunday 2am, 4pm, or 11pm. Venus rules over friendship, and these are the hours of the day venus rules. so casting during the waxing-full moon, on friday at 3 [or sunday and 2 or whenever listed above] would be best.