Waxing Moon vs Waning Moon

With a new Moon on day 0, a person drafts a short report during the waxing half, up to the full Moon near day 15, then edits and sends it by day 30.

A waxing Moon is growing: more of its visible face is lit each night, heading toward full. A waning Moon is shrinking, heading toward new. Each half of the cycle lasts about 14.8 days, and the rest of this article is about telling them apart on sight and deciding what, if anything, to do with the difference.

From the Northern Hemisphere, the waxing Moon is lit on its right side and the waning Moon is lit on its left. From the Southern Hemisphere the view is flipped, so a waxing Moon is lit on the left. Near the equator the Moon often appears tipped so a crescent looks like a bowl or a boat on its back, and the side rule is harder to use.

The time the Moon is in the sky works in every hemisphere. A waxing Moon is in the afternoon and evening sky, and a waning Moon rises late and is still visible in the morning. Use this three-check test.

1. Check the time. Visible in the evening after sunset: waxing. Visible in the early morning: waning.
2. Check the lit side, remembering your hemisphere. In the Northern Hemisphere a lit right side means waxing, and in the Southern Hemisphere a lit left side means waxing.
3. Check a calendar. If the next full Moon comes before the next new Moon, the Moon is waxing. If the next new Moon comes first, it is waning.

The table pulls the main differences into one place. The timing in the last rows is approximate and follows from the Moon’s position relative to the Sun.

Astrological and ritual traditions give the two halves complementary jobs. The waxing half is associated with beginning, building, adding and learning, because the visible light is increasing. The waning half is associated with clearing, finishing, editing and resting, because it is decreasing.

These are symbolic assignments. The Moon’s light does not change how well you can start or finish a task. What the assignment offers is a division of labor: two weeks to build something, two weeks to tidy and complete it.

The full Moon and the new Moon sit at the hinges. The full Moon is the turning point from adding to subtracting, and the new Moon is the turning point back. Some people treat those two nights as review days, one looking at what to take on and the other at what to put down.

The first benefit is clear planning. Splitting a month in two reduces decisions: during the waxing half you take on, and during the waning half you review and close. Many people find that a simple rule helps them keep a rhythm.

The second benefit is avoiding mix-ups. A crescent at 30 percent lit could be waxing or waning, so the percentage alone does not tell you the direction. Use the lit side, the time of day or a calendar. The word gibbous is also easily confused with full: a gibbous Moon is more than half lit but not yet full.

Say a new Moon falls on day 0. A quarter of the 29.5-day cycle is about 7.4 days, so first quarter is near day 7, the full Moon near day 15 (14.8 days), last quarter near day 22 (22.1 days) and the next new Moon near day 30.

A person writing a short report might build in the waxing half, drafting sections between day 0 and day 15. In the waning half they edit, cut and send it between day 15 and day 30. The Moon does not help the report; the two-part schedule does.

A few misunderstandings come up again and again.

• Assuming waning means bad. It is a half of the cycle, not a warning.
• Using the lit-side rule in the wrong hemisphere and reading waning as waxing.
• Treating the division as strict. Nothing prevents you from starting something during the waning half.
• Reading the percentage as the direction. Half lit can be first quarter or last quarter.

Step outside, note the time, and look at which side of the Moon is lit. Then open a Moon phase calculator and confirm whether it is waxing or waning. Do it for a few nights and the pattern becomes automatic.

Try the three checks on these constructed observations before you go outside. The last row shows why a single clue is not enough.

Why does the Moon rise later each night? It moves east against the stars by about 13 degrees a day, so it rises about 50 minutes later each day on average. That drift carries the waxing Moon from the afternoon sky into the late evening sky as the weeks pass.

Is there a quick way to remember the sides? In the Northern Hemisphere a lit right side looks like the curve of a D and a lit left side like the curve of a C. The letters D, O, C follow the order of the cycle: growing, full, shrinking. The trick fails in the Southern Hemisphere, where the lit sides are swapped.

Does waxing include the night of the full Moon? The full Moon is the turning point between the halves, so it belongs to neither. Waxing ends at the instant of full Moon and waning begins at once. The same is true of the new Moon in the other direction.

The building and clearing jobs given to each half are symbolic, and a lit percentage alone cannot tell you which half you are in.