Guide
The 24 solar terms
Why your Chinese month can change several days into a Western month, which boundaries alter a pillar, and what that means in your reading.
The dates in your reading come from the Sun
The solar terms divide the Sun's yearly path into 24 equal steps. Twelve open BaZi months. The twelve between them mark the middle of those months. This is why a Chinese month often turns around the fourth to eighth day of a Western month.
For you, the opening terms are the important chart boundaries. Crossing one can change the month pillar used for a birth or a current reading. The midpoint terms add seasonal context, but they do not replace that pillar.
Start of Spring
立春 · Lì Chūn
Around February 3
Opens a BaZi month
The seasonal cycle begins turning toward growth.
This opens the Tiger month and the BaZi year. A January or early-February birthday may therefore belong to the previous pillar year.
Rain Water
雨水 · Yǔ Shuǐ
Around February 18
Midpoint of a BaZi month
Wintry precipitation begins giving way to rain.
This marks the middle of the Tiger month. It changes the season's emphasis, but it does not create a new month pillar.
Awakening of Insects
惊蛰 · Jīng Zhé
Around March 5
Opens a BaZi month
Warming ground and early thunder signal renewed activity.
This opens the Rabbit month. A reading dated in early March changes here, not on March 1.
Spring Equinox
春分 · Chūn Fēn
Around March 20
Midpoint of a BaZi month
Day and night reach near-equal length.
This divides the Rabbit month and marks equal daylight. It locates the person within that month without replacing its pillar.
Clear and Bright
清明 · Qīng Míng
Around April 4
Opens a BaZi month
Air clears and spring growth becomes more visible.
This opens the Dragon month. Someone born on either side of this boundary can have a different month pillar despite sharing a calendar month.
Grain Rain
谷雨 · Gǔ Yǔ
Around April 19
Midpoint of a BaZi month
Rain arrives at a point associated with nourishing grain.
This marks the middle of the Dragon month. It describes where the season stands, while the same month pillar continues.
Start of Summer
立夏 · Lì Xià
Around May 5
Opens a BaZi month
The seasonal cycle turns toward heat and outward growth.
This opens the Snake month and the summer quarter. Its arrival changes the seasonal setting around every Day Master.
Grain Buds
小满 · Xiǎo Mǎn
Around May 20
Midpoint of a BaZi month
Grain begins filling but has not yet ripened.
This marks the middle of the Snake month. It helps place current timing within the month rather than beginning a new one.
Grain in Ear
芒种 · Máng Zhòng
Around June 5
Opens a BaZi month
Awned grain reaches harvest and planting work intensifies.
This opens the Horse month. A June reading turns here because BaZi follows the Sun's position, not the numbered month.
Summer Solstice
夏至 · Xià Zhì
Around June 21
Midpoint of a BaZi month
Daylight reaches its yearly maximum in the northern hemisphere.
This divides the Horse month at the year's longest daylight. The month pillar holds while the seasonal balance reaches an extreme.
Minor Heat
小暑 · Xiǎo Shǔ
Around July 6
Opens a BaZi month
Summer heat becomes established.
This opens the Goat month. The change matters when the Goat branch supports, repeats, or presses something in the birth chart.
Major Heat
大暑 · Dà Shǔ
Around July 22
Midpoint of a BaZi month
The hottest seasonal interval arrives.
This marks the middle of the Goat month. It refines the timing but does not create another pillar.
Start of Autumn
立秋 · Lì Qiū
Around August 7
Opens a BaZi month
The cycle begins turning from expansion toward harvest.
This opens the Monkey month and the autumn quarter, even when the weather still feels like summer where the reader lives.
End of Heat
处暑 · Chǔ Shǔ
Around August 22
Midpoint of a BaZi month
The strongest summer heat begins to recede.
This marks the middle of the Monkey month. It names movement within the season rather than a new chart instruction.
White Dew
白露 · Bái Lù
Around September 7
Opens a BaZi month
Cooler nights make morning dew more visible.
This opens the Rooster month. A September reading changes here, several days after the Western month begins.
Autumn Equinox
秋分 · Qiū Fēn
Around September 22
Midpoint of a BaZi month
Day and night return to near-equal length.
This divides the Rooster month at equal daylight. It gives seasonal context while the Rooster pillar remains in place.
Cold Dew
寒露 · Hán Lù
Around October 8
Opens a BaZi month
Dew forms in noticeably colder air.
This opens the Dog month. If Dog repeats or meets another branch in a chart, that relationship becomes more available to notice now.
Frost's Descent
霜降 · Shuāng Jiàng
Around October 23
Midpoint of a BaZi month
The first frosts become seasonally possible.
This marks the middle of the Dog month. It places the reading later in the same period rather than starting a new one.
Start of Winter
立冬 · Lì Dōng
Around November 7
Opens a BaZi month
The cycle turns toward storage and shorter days.
This opens the Pig month and the winter quarter. The seasonal setting changes before the Western calendar calls it winter.
Minor Snow
小雪 · Xiǎo Xuě
Around November 22
Midpoint of a BaZi month
Early snow becomes possible in northern climates.
This marks the middle of the Pig month. It describes the season's progress while the Pig month continues.
Major Snow
大雪 · Dà Xuě
Around December 7
Opens a BaZi month
Cold deepens and accumulating snow becomes more likely.
This opens the Rat month. A December reading turns here, when the Sun reaches the calculated boundary.
Winter Solstice
冬至 · Dōng Zhì
Around December 21
Midpoint of a BaZi month
Night reaches its yearly maximum in the northern hemisphere.
This divides the Rat month at the longest night. It marks a seasonal extreme, not the beginning of a new BaZi year.
Minor Cold
小寒 · Xiǎo Hán
Around January 5
Opens a BaZi month
Deep winter cold becomes established.
This opens the Ox month, the last month before Start of Spring. January still belongs to the current BaZi year here.
Major Cold
大寒 · Dà Hán
Around January 20
Midpoint of a BaZi month
The final cold interval arrives before the spring cycle begins again.
This marks the middle of the Ox month. The next BaZi year does not begin until Start of Spring.
What to look for in your chart
Check whether your birthday falls close to Start of Spring or one of the monthly opening terms. Then look at the exact boundary for your birth year before deciding which pillar belongs to you. For current timing, read the new month against your Day Master and the rest of your chart rather than treating the term as general advice for everyone.
See how Aster applies the boundary in a monthly reading, or calculate your four pillars.