Moon Phase Names by Lunar Day: Crescent, Jusanya, Izayoi and the Japanese "Waiting Moons", Moon Age vs Lunar Day, Harvest Moon Timing and the Moon on Your Birthday

The short answer: most moon names come from the day of the lunar month

Most traditional moon names are attached to the lunar day: the day of the lunar month, counting the day of the new moon as day 1. In the old East Asian lunisolar calendar, the new moon always fell on the 1st, so the lunar day is simply the date in that calendar. Mikazuki is the moon of day 3, jusanya the moon of day 13 and jugoya the moon of day 15. Here are the main names with a rough guide to when and where to look (moonrise times assume sunset at 6 p.m. and shift with the season and your location).

The "moon age at noon" column shows that the moon age at noon is roughly the lunar day minus 1. Moon age is a decimal counted from the moment of the new moon; the lunar day is a whole number counted by calendar date. The two never match exactly, so "moon age 15" does not mean "jugoya", and the full moon actually lands on day 16 more often than day 15. More on that below.

The phases of the moon in order: the eight shapes

The moon gives off no light of its own; the half facing the sun is lit. As the moon orbits Earth, we see more or less of that lit half, and the moon cycles from new moon to crescent, first quarter, full moon, last quarter and back to new moon in about 29.5 days. That cycle is the synodic month. By shape, it splits into four instants and the four stretches between them, eight phases in all.

New moon, first quarter, full moon and last quarter are instants whose times astronomers calculate to the minute. In November 2026 (US Eastern time), the last quarter is on the 1st at 3:28 p.m., the new moon on the 9th at 2:02 a.m., the first quarter on the 17th at 6:48 a.m. and the full moon on the 24th at 9:53 a.m. The day that contains one of these instants is called the "first quarter day" or "full moon day"; every other day shows a shape on the way to or from one of them.

In Japanese and Chinese, the quarters are called the "upper string" and "lower string" moons, picturing the straight edge of the half moon as a bowstring. The first quarter moon is due south at dusk, and when it sets around midnight its straight edge points up; the last quarter rises around midnight with its straight edge pointing down. Because the edge's angle changes through the night, the reliable rule is this: lit on the right means first quarter (getting fuller), lit on the left means last quarter (getting thinner).

Moon age vs lunar day: what's the difference?

Moon age is the number of days, as a decimal, since the most recent new moon. It is 0 at the moment of the new moon and goes up by 1 each day. The moon age on calendars and in almanacs is the value at noon that day. The lunar day, by contrast, is a whole number: the day containing the new moon is day 1, and the time of day doesn't matter. Comparing them for November 2026 (US Eastern time) shows how they differ.

On the day of a new moon, the noon moon age is in the 29s (the end of the previous cycle) if noon comes before the new moon, and in the 0s if it comes after. The lunar day counts by date, so the new moon day is day 1 whether the new moon falls in the morning or at night. That's why noon moon age and lunar day are about 1 apart, and can be nearly 1.5 apart depending on the time of the new moon.

So which lunar day does the full moon fall on? The gap from new moon to full moon isn't fixed. Because the moon's orbit is an ellipse, it ranges from about 13.9 to 15.6 days. Counting the 383 full moons from 2000 to 2030 in US Eastern time, the full moon day was lunar day 15 150 times (about 39%), day 16 173 times (about 45%), day 17 58 times (about 15%) and day 14 just twice (about 0.5%). Because the new moon day counts as day 1, a full moon an average of 14.8 days later tends to land on day 16.

The length of the cycle varies too, from about 29.3 to 29.8 days, averaging 29.530589 days. That is why lunar calendar months alternate between 29-day "short" and 30-day "long" months, and only long months have a lunar day 30.

Izayoi and the "waiting moons": why moonrise is about 50 minutes later every night

The Japanese names for the nights after the full moon describe how people waited for it to rise. The moon moves about 12 degrees east along its orbit each day, so Earth has to turn a little extra before the moon comes up again, and moonrise gets about 50 minutes later each night on average.

The delay varies a lot by season. At mid-northern latitudes, the moon's path meets the horizon at a shallow angle around the autumn full moon, so the delay shrinks to around 30 minutes and the moon rises near dusk several evenings in a row. That's the origin of the name Harvest Moon for the full moon closest to the autumn equinox: bright moonlight right after sunset for several nights let farmers keep working. Around the spring full moon, by contrast, the delay can exceed an hour.

In Edo-period Japan, people gathered on set nights of the lunar month to wait for moonrise, a custom called tsukimachi ("moon waiting"). There were thirteenth-night, nineteenth-night and twenty-third-night gatherings; the twenty-third-night vigil, for the last quarter moon rising at midnight, left behind stone markers called nijusanya-to that still stand across Japan. On the 26th night of the seventh lunar month, crowds filled the shores of Shinagawa and Takanawa in Edo to see the thin dawn crescent, in which the Amida Buddha and two attendants were said to appear.

More moon names: evening moon, dawn moon, hazy moon and the full moon names

Besides the names tied to the lunar day, Japanese has names based on the time of night, the season or the sky. Many are seasonal words in haiku, and "moon" on its own means autumn.

The full moon names now popular worldwide, like Strawberry Moon and Harvest Moon, come from North American farmers' almanacs. From January they are the Wolf Moon, Snow Moon, Worm Moon, Pink Moon, Flower Moon, Strawberry Moon, Buck Moon, Sturgeon Moon, Corn Moon (or Harvest Moon), Hunter's Moon, Beaver Moon and Cold Moon. The full moon nearest the autumn equinox becomes the Harvest Moon and the next one the Hunter's Moon, so they fall in September or October depending on the year.

A color in the name doesn't mean the moon looks that color. The Strawberry Moon is the full moon of the strawberry harvest, and the Pink Moon is named for spring flowers. Still, the June full moon follows the lowest path across the Northern Hemisphere sky of the year, so the atmosphere often gives it a reddish or orange tint, and that overlap helped the name catch on. A "Blue Moon", the second full moon in a calendar month, is about rarity (roughly once every 2.7 years), not color either.

When are jugoya, jusanya and tokanya? Moon-viewing nights vs the full moon (2026–2030)

Japan's moon-viewing nights follow the lunar calendar. Jugoya (the harvest moon of mid-autumn) is the 15th day of the 8th lunar month, jusanya (the "later moon") is the 13th day of the 9th month and tokanya is the 10th day of the 10th month. The 8th lunar month is defined as the month containing the autumn equinox, the 9th the month containing the solar term Soko (frost descent, around October 23) and the 10th the month containing Shosetsu (minor snow, around November 22), so the dates can be calculated from new moons and the solar terms. The table uses Japan time.

After 2021–2023, jugoya and the full moon next fall on the same day in 2030–2032. Even in a year like 2026, when they are two days apart, more than 90% of the jugoya moon is lit, so it looks almost round. Jusanya comes two or three days before the full moon, with a little missing on the left, and admiring a moon that is "not yet full" has long been part of its appeal.

• Jugoya is also called imo-meigetsu ("taro moon"), with taro and other autumn crops offered to the moon. Many regions stack 15 rice dumplings for the fifteenth night.
• Jusanya is also called kuri-meigetsu ("chestnut moon") or mame-meigetsu ("bean moon"), with chestnuts or edamame as offerings. It is a Japanese custom with no counterpart in China or Korea.
• Viewing only one of jugoya and jusanya is called katami-zuki ("one-sided moon viewing"), and tradition says it brings bad luck.
• Tokanya is a harvest festival mainly in eastern Japan; besides moon viewing, children beat the ground with straw bundles to send off the rice-field god.

How to find the moon on the day you were born, and the years your birthday is a full moon

The same calculation tells you what the moon looked like on the day you or your child was born. With just a date you get the moon age at noon; with a time of birth you get the moon age at that moment. In the Moon Phase Calendar & the Moon on Your Birthday tool:

1. 1

   Enter the date under "The moon on the day you were born"

   Enter the birth date or anniversary. If you know the time of birth, add it under "Time (if known)"; leave it blank to use the moon age at noon.

2. 2

   Choose the time zone of the birthplace

   Pick the time zone where the birth happened, such as "US Eastern (New York)". A new or full moon can fall on a different date in different time zones.

3. 3

   Read the shape, moon age, lunar day and name

   Alongside the drawing of the moon you'll see the moon age, illumination, lunar day and that day's traditional name with its meaning. "Save moon image (PNG)" turns it into a picture for a birthday card or post.

4. 4

   Check "Years your birthday is a full moon"

   This lists which of your 1st to 100th birthdays contain a full moon, and which fall on the same lunar day as the day you were born.

Take August 20, 2010 (US Eastern time): the moon was 10.5 days old at noon, on lunar day 12, a waxing gibbous about 86% lit. For someone born that day, the 2013, 2032 and 2043 birthdays are full moons, and the 2029, 2048 and 2067 birthdays fall on the same lunar day 12 as the birth date. The same shape returns every 19 years because 235 synodic months (about 6,939.69 days) almost equal 19 years (about 6,939.60 days). This is the Metonic cycle.

The match is only "almost", though. Since 235 synodic months run about 2 hours longer than 19 years, the phases slip about 2 hours later on the calendar every 19 years. The number of leap days in between (4 or 5) also nudges things by up to a day, so 19 years later the lunar day can be off by one, and full moon birthdays don't always keep coming every 19 years. In the example, the gap from 2032 to 2043 is 11 years.

Things to keep in mind when watching or looking up the moon

• Moonrise and moonset times shift by tens of minutes with your latitude, longitude and the season. The times in this guide are rough guides; for exact times, use an almanac or a moonrise calculator set to your location.
• The full moon's size changes with its distance, from about 356,000 to 406,000 km. The closest full moon looks about 14% larger and about 30% brighter than the farthest. In US Eastern time, the biggest full moon of 2026 is on December 23 and of 2027 on January 22.
• For Milky Way or night-sky photography, choose a few days either side of the new moon. Knowing the lunar day tells you, for example, that a day-3 crescent will have set by about 8 p.m. For settings, see camera settings for the Milky Way.
• A date in the lunar calendar is the lunar day plus the month number and leap-month rules. The Japanese rokuyo calendar signs are also set from the lunar month and day; see the meanings and order of rokuyo if you're curious how.

FAQ

What's the difference between jusanya and izayoi?

Jusanya is the moon of lunar day 13, about two days before full, with a little missing on the left. Izayoi is the moon of day 16, right after the full moon or the full moon itself; it rises about 50 minutes later than the night before, so it was called the "hesitating" moon. Jusanya on the 13th day of the 9th lunar month is also a moon-viewing night in Japan.

Which lunar days are tachimachi, imachi, nemachi and fukemachi?

Tachimachi-zuki is day 17, imachi-zuki day 18, nemachi-zuki (fushimachi-zuki) day 19 and fukemachi-zuki day 20. Moonrise gets about 50 minutes later every night after the full moon, so people named them by how they waited: standing, sitting, lying down, and until late at night.

Is a moon age of 15 a full moon?

The full moon comes at an average moon age of 14.8, so a moon age around 15 means the full moon or a day either side. But the gap from new to full ranges from 13.9 to 15.6 days, so a day with a noon moon age of 15 can be the day after the full moon. Check the full moon's date and time to be sure.

Which is right: moon age or lunar day?

Both are right; they count differently. Moon age is the time since the new moon as a decimal; lunar day is the calendar date, with the new moon day as day 1. The noon moon age is roughly the lunar day minus 1. Traditional names like mikazuki, jusanya and izayoi come from the lunar day.

Which lunar day does the full moon usually fall on?

Day 16 is the most common. Counting full moons from 2000 to 2030 in US Eastern time, about 45% fell on day 16, about 39% on day 15 and about 15% on day 17. Because the new moon day counts as day 1, a full moon an average of 14.8 days later tends to land on day 16.

How do I tell a first quarter moon from a last quarter moon?

From the Northern Hemisphere, a half moon lit on the right is first quarter and one lit on the left is last quarter. The first quarter is in the southern sky at dusk; the last quarter is in the southern sky at dawn. In the Southern Hemisphere, left and right are reversed.

When are jugoya and jusanya in 2026 and 2027?

In 2026, jugoya is September 25 and jusanya October 23. In 2027, jugoya is September 15 and jusanya October 12 (Japan time). The 2026 jugoya is two days before the full moon, and the 2027 one is the day before.

How often is a birthday a full moon?

About once every 30 years on average. Moon phases return to nearly the same dates every 19 years, so full moon birthdays often come 19 years apart, sometimes 11 or 8. The Moon Phase Calendar & the Moon on Your Birthday tool lists which of your first 100 birthdays are full moons.

Can I find my birthday moon without knowing my time of birth?

Yes. Without a time, the tool uses the moon age at noon. The time of birth changes the moon age by at most about 0.5; the lunar day, the name and the visible shape hardly change.