This algorithm is slightly less than perfect. To even out the quiz results I'm assuming the short phases (full/new moon, quarters) last just as long as the transitional phases (waning crescent). I mean come on how many times have you looked up at a full moon and wondered if it was really only 98% illuminated?
In addition, if you were born in between phases it might be a bit off because it doesn't consider the location, time of day, or timezone you were born in. If you care deeply there are more accurate ways to get this information (like this).
Also, my algorithm does not take into consideration the fact that the sun's gravity sometimes makes the moon's orbit more or less eccentric, changing the length of a synodic month by nearly 13 hours. So while the algorithm is good if you were born in recent history, it may drift off if you're a vampire or something, so you should consult NASA's tables of moon cycles covering the last 6000 years.
Final note: the personality descriptions are based on astrology, which is not really scientific. But you probably know that.