White Dew

Meaning

White Dew, Bailu, is the fifteenth of the twenty-four solar terms: the Sun at 165°, about 8 September. The nights have grown cool enough for dew to gather thickly on the grass, white in the early light. White is also the colour of Metal, the phase of autumn, and the name joins the two: the season’s own colour lying on the fields at dawn.

It is an opening term: it opens the Rooster month, the eighth solar month, the heart of autumn and of Metal, whose branch, You, is Metal at its purest. The harvest is under way, the air is dry and clear, and the difference between the day’s warmth and the night’s cool is at its widest.

Its three pentads belong to the birds: the wild geese arrive from the north, the swallows leave for the south, and the birds of the fields lay up their stores for winter.

In practice

• In BaZi a birth from this instant belongs to the Rooster month and its pillar; a birth within five minutes of it is marked uncertain, since a slightly different time would give the Monkey month.
• In Chinese astrology the month animal turns from the Monkey to the Rooster, and the Cycles lens begins the Rooster month’s reading here.
• In Feng Shui the month’s star changes, one less than the Monkey month’s.
• The Calendar marks it on its day, with the Sun at 15° Virgo, as the opening of the Rooster month.

Across traditions

• In Western astrology the Sun is at 15° Virgo, the middle of the harvest sign, and the full moon of these weeks or the next is the harvest moon, whose light once let farmers work late into the evening.
• In Japan, Korea and Vietnam the term is hakuro, baengno and bạch lộ; in Japan the season of moon-viewing, tsukimi, is close.
• In the vineyards of Europe the same weeks bring the grape harvest, and the morning dew on the vines is a sign the winegrowers watch as closely as the Chinese almanac does.

Origin and history

The white dew is one of the oldest images of autumn in Chinese poetry. The Book of Songs, in the poem “Reeds”, sets its scene in the cold of early autumn, “the reeds are green and grey, the white dew turns to frost”, and the line has been quoted for every autumn longing since. The “Twelve Months” of the Lüshi Chunqiu gives the term’s signs, and the Huainanzi, in 139 BC, its place among the twenty-four.

In the tea country of the south, the tea picked around White Dew has its own name and its own lovers, rounder and gentler than the spring tea. Many households begin to air the winter clothes and to change the bedding, and in the countryside the harvest of the autumn crops fills the threshing floors.

How Ulune calculates it

Ulune takes White Dew as the instant the Sun’s apparent longitude reaches 165°, from its table of the solar terms computed with the Swiss Ephemeris for 1800 to 2200. The Rooster month and its pillar begin at that instant, whatever the clock or the time zone. In 2026 it fell on 7 September at 14:41 UT.

Correspondences