a moon phase occurs 28 days after the last time it occurred
new_moon is phase_of_moon. phase_of_moon is not phase. phase_of_moon is time_period. phase_of_moon is not time_period. moon has not phases moon's_orbital_period_around_earth is not 28_days. moon has phases moon's_orbital_period_around_earth is 28_days. phase_of_moon is phase. new_moon is not phase_of_moon.