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.
how long do the moon phases last
Each moon phase lasts for only an instant as the moon constantly moves.

Question: how long does it take for all the phases to be completed
Self-contained rewrite: how long does it take for all the moon phases to be completed