Good for victory and for contests, for litigation and for the taking of vows, and for the worship of Krishna and of the Goddess. Popular practice avoids it for marriage and for some other samskaras.
Meaning
Ashtami is the eighth tithi. Its adhidevata is Vasudeva (Krishna), whose birth falls on the eighth of the dark fortnight of Bhadrapada, and the Goddess is worshipped on the eighth of the bright fortnight of the Navaratri. It is a Jaya tithi, of victory, and it is also the tithi most often avoided in practice.