Conversation so far:
what comes 14 days after a full moon
what comes 14 days after a new moon
14 days after the new moon, we see a full moon.
how many phases of the moon are there
The moon has eight phases, new moon, waxing crescent, first quarter, waxing gibbous, full moon, waning gibbous, last quarter and waning crescent.

Question: how long do the phases last
Self-contained rewrite: how long do the moon phases last