Is the moon waxing or waning?

Recently while looking at a crescent moon at sunset, someone asked me: waxing or waning? To my great chagrin, my answer was wrong. 

If I had noticed a new moon on a previous day, then the answer would obviously be waxing. But there’s another way to get the correct answer. 

When seen about the time of sunset, the moon is always waxing, and a quarter moon is always 1st quarter. Whatever moon phase that you see about the time of sunset, you can be sure that at the next sunset, the moon will illuminate more area until it gets to full. 

This diagram shows the range of possible moon phases at sunset. 

Imagine yourself at the center bottom dot of this and the other diagrams. Check the post of 3/24 for moon images.

When seen about the time of sunrise, the moon is always waning and a quarter moon is always 3rd quarter. Whatever moon phase you see about the time of sunrise, you can be sure that at the next sunrise the moon will illuminate less area until it gets to new. 

This shows the range of possible moon phases at sunrise. ​

See the post of 3/24 for images of the moon at various phases

At midnight if the moon is in the east (rising) then it is waning; if it is in the west (setting) then it is waxing. 

​This shows the range of possible moon phases at midnight.

See the post of 3/24 for images of the moon at various phases

SUMMARY