Bailu (白露), White Dew, begins in 2027 at the precise moment of 04:28 on September 8, Beijing time (UTC+8), when the sun reaches 165° celestial longitude. It is the fifteenth of the 24 solar terms and the moment the calendar announces what the mornings have been hinting: summer is over, and the first condensation appears on grass as white dew.
Key Takeaways
- Bailu 2026 arrived at 22:41 on September 7; Bailu 2027 begins at 04:28 on September 8, both computed to the minute at 165° celestial longitude
- The name records a physical fact: nights now cool enough to condense vapor into visible dew, the calendar’s announcement that autumn’s air has arrived
- Bailu is a boundary term that opens the Rooster month (酉月) in BaZi, switching the month pillar at the exact minute
- Classical phenology records three pentads: wild geese arrive, swallows depart, and birds begin storing food
- The season’s most quoted health advice is born here: “show no flesh at White Dew” (白露身不露), the end of summer clothing
What Is Bailu, the White Dew Solar Term?
Bailu is the third term of autumn, arriving after the Limit of Heat (Chushu) and before the Autumn Equinox (Qiufen). The name is observational physics compressed to two characters: as nights lengthen and cool through late August and early September, surface temperatures drop below the dew point, and atmospheric moisture condenses on grass, leaves, and spider webs as droplets that scatter the morning light white. The classical gloss in the Yueling Qishier Hou Jijie explains the color word directly: spring’s dew is unclear, autumn’s condenses white (春露不明，秋露凝白), because the temperature gap between day and night is now wide enough to mark the change of season in water.
The term is the calendar’s precision instrument for a transition that thermometers confirm: the diurnal spread widens through this fortnight, with north China commonly seeing 10°C between afternoon and pre-dawn. Farmers read it as the grain-filling stretch’s final phase and the cue that wet-field work ends; poets read it as the year’s first image of transience. The Book of Songs’ oldest stratum contains the line that has anchored a thousand later poems, “white dew, the frost” (白露为霜), the moment condensation will harden toward the frost of the term after next. The solar term system as a whole holds UNESCO intangible cultural heritage status, with official English terminology at the China Culture archive.
The Exact Moment Bailu Begins in 2026 and 2027
References print “September 7-9”; the almanac engine gives the minute, and at Bailu the minute is a month-pillar boundary:
| Year | Exact Moment (UTC+8) | Sun’s Celestial Longitude | Month Pillar Switch |
|---|---|---|---|
| 2026 | September 7, 22:41 | 165° | Bing Shen (丙申) → Ding You (丁酉) |
| 2027 | September 8, 04:28 | 165° | Wu Shen (戊申) → Ji You (己酉) |
Both instants come from the 12Zodiacs almanac engine on JPL DE440s ephemeris data. The 2026 boundary landed at 22:41, meaning charts stamped the evening of September 7 sat on the Monkey-month side until eleven minutes before midnight, then flipped within the same date. The 2027 moment converts to 20:28 UTC on September 7, which is mid-afternoon in the Americas: another case of the two hemispheres honestly printing different dates for the same instant.
In practice, the minute decides the Rooster month. A chart for September 7, 2026 at 22:00 carries the Monkey month (申月) with its three hidden stems; from 22:41 onward the Rooster month (酉月) with its single pure Xin Metal applies, a switch that changes the month branch’s entire hidden-stem structure. The 12Zodiacs daily almanac publishes the boundary to the minute.
The Three Pentads: Arrivals, Departures, Provisions
The Yizhoushu phenology for Bailu reads as the migration calendar:
| Pentad | Chinese | English | Phenology Type |
|---|---|---|---|
| First (days 1-5) | 鸿雁来 | Wild geese arrive from the north | Animal |
| Second (days 6-10) | 玄鸟归 | Swallows return south | Animal |
| Third (days 11-15) | 群鸟养羞 | Birds begin storing provisions | Animal |
The ledger runs as spring’s mirror in flight: the swallows that the spring equinox’s second pentad welcomed now leave, and the geese that left in spring now return from the far north, the two species passing in opposite directions through the same fortnight. The third pentad generalizes the instinct: xiu (羞) in the classical usage means provisions, and resident birds shift from breeding behavior to caching. What stands out about the sequence is its completeness: within fifteen days the phenology records arrival, departure, and storage, the full logistics of a season change, which is why ancient coastal and wetland communities keyed their own harvest-and-preserve calendars to the same window.
Longan Tea, White Dew Tea, and the Turning Table
Bailu’s customs are quieter than the festival terms, focused on the table and the apothecary:
| Custom | Practice | Region / Logic |
|---|---|---|
| White Dew tea | Picking autumn tea between Bailu and the equinox | The summer’s bitterness gone, the leaves sweetening in the cool nights; prized above spring pick by old Suzhou drinkers |
| White Dew rice wine | Brewing glutinous millet wine at the term | Hunan, Jiangsu; mild, served warm to guests through autumn |
| Longan with rice porridge | Eating longan with thin congee | Fuzhou; the fruit’s last and best window, a local belief in its Bailu-day potency |
| Ten Whites (十样白) | Gathering ten herbs and roots whose names contain “white” | Zhejiang; cooked with a white-boned duck for the joints |
| Collecting the dew | Wiping morning dew from herbs and petals into vessels | Ming-dynasty apothecary practice; the Compendium of Materia Medica records dew as a medicinal carrier |
The ten-whites custom is the term’s most charming pharmacology: Baihe (lily), Baimao (cogon grass), Baimu (white atractylodes), and seven more “white” botanicals, assembled on the logic that the white-dew day amplifies whatever shares the term’s color, a sympathetic-medicine rule of thumb rather than biochemistry, still practiced as community cookery. The dew-collecting tradition has the most surprising afterlife: Li Shizhen’s sixteenth-century pharmacopoeia classified dew gathered from different plants as carrying different properties, and the practice persists in scattered form wherever herbalists keep old habits. We recommend the tea rather than the duck: the autumn pick’s window is real, two weeks when the leaf balances sweetness against the fading year, and the tea shops that mark it are keeping accurate time.
Bailu in Your BaZi Chart: The Rooster Month Opens
For BaZi practice, Bailu is the boundary that opens the Rooster month (酉月), the season the autumn equinox article described at its midpoint. In the 2027 season the switch at 04:28 on September 8 moves the month pillar from Wu Shen (戊申) to Ji You (己酉), and the technical interest lies in the contrast across the boundary: the Monkey branch hides three stems, Geng (庚) Metal dominant, Ren (壬) Water secondary, and Wu (戊) Earth residual, a mixed structure the classics read as versatile and restless, while the Rooster branch holds a single pure Xin (辛) Metal, refined and single-minded. Charts flip at this minute from a month of mixed cargo to a month of one pure note.
The switch matters most for Metal Day Masters, whose strengthening season begins at this boundary rather than at the equinox, and for Wood Day Masters, whose pruning season opens here. September births within a day of the term need the minute-level check: a chart stamped September 7, 2026 at 22:00 is a Monkey-month chart with Water available in its hidden stems; at 23:00 the same evening it is a Rooster-month chart without that Water, a difference that changes drought-resistance readings in Wood-heavy charts. In Mei Lin Chen’s practice, the Bailu fortnight is when clients in education and publishing schedule their year’s launches, the metal-blade season that cuts through noise, a timing habit one Monkey-month publisher attributed to superstition and kept anyway after three consecutive years of clean launches. The Rooster year pages profile the month’s branch, and the auspicious dates calendar applies the boundary to event planning.
What to Do and What to Avoid Around Bailu
Practical guidance for the term:
- Cover the extremities from now on. The maxim “show no flesh at White Dew” (白露身不露) ends the bare-ankle season; the autumn-freezing doctrine applies to mild exposure only, and the neck, wrists, and ankles get sleeves and socks.
- Shift the plate toward moisture. Pear, lily bulb, white fungus, honey, and sesame answer the drying air; the crab that fattens from now can join in moderation.
- Adjust sleep toward the light. The classical autumn schedule eases bedtimes earlier and rises with the rooster, matching the shortening days rather than fighting them.
- Check September birthdays against the minute. Charts near September 7-8 straddle the Monkey-Rooster boundary; the BaZi calculator resolves the side in one step.
- Buy the tea, note the wine. The White Dew pick and the home-brewed rice wine are the term’s two genuine consumables, both time-boxed to this fortnight.
Why do some autumn mornings show dew only after Bailu, never before?
The physics is the dew point. Dew condenses whenever a surface cools below the temperature at which air saturates, and through early autumn the nights are still too warm and long-day surfaces hold too much heat for that crossing. By the Bailu fortnight, nights have lengthened enough and the air’s moisture profile has shifted enough that grass and leaf temperatures drop below saturation in the pre-dawn hours, and the condensation becomes visible as scattered droplets; the calendar’s observation is exact, recording when dew becomes routine rather than when it becomes possible, which is why the classical gloss emphasizes the whiteness and regularity rather than the existence of droplets.
How does Bailu relate to the Autumn Equinox that follows two weeks later?
The two terms divide the labor of autumn’s opening: Bailu is the boundary term that switches the almanac month, opening the Rooster month and marking the first routine condensation, while Qiufen is the major term at the month’s midpoint, marking the global light-dark balance. In BaZi terms, Bailu is the switch and Qiufen the peak: charts change their month pillar at Bailu’s exact minute, seasonal-strength analysis treats the equinox week as the Metal season’s flood, the phenology mirrors the division with Bailu’s pentads tracking birds while the equinox’s track thunder and water, and the old health maxim splits the season the same way, dressing warnings at Bailu and drying-air remedies from the equinox on.
Can the Monkey-to-Rooster switch change chart readings despite birthdays far from the boundary?
The switch changes the seasonal context for every chart, not only those born on the boundary dates. Once the Rooster month commands, pure Xin Metal weights the season’s strength analysis, so a Metal Day Master born anywhere in the year reads as more in-season for events scheduled now, and a Wood Day Master reads as more challenged, regardless of their own birth month. Practitioners use the boundary weeks to re-time annual plans, launches into the Metal month for cutting through and consolidations held back to the Water months, because the chart itself never changes while the weather around it does, and the solar calendar is that weather report.
Conclusion
Bailu is the calendar proving autumn with water: one clear morning of white droplets, geese overhead, swallows gone, and the Rooster month open at the minute. The 2027 term arrives at 04:28 on September 8 Beijing time, the Metal season begins its purest stretch, and the long sleeves come out on schedule. To see which side of the boundary your own September chart falls on, try the 12Zodiacs BaZi Calculator, and for every term switch through the autumn, follow the Tung Shing almanac.
Sources
- Bailu (solar term), Wikipedia (term definition, dates)
- The Twenty-Four Solar Terms, UNESCO Intangible Cultural Heritage (heritage listing)
- Solar Terms, China Culture, Ministry of Culture (official English translations)
- Solar term timing data computed by the 12Zodiacs almanac engine (JPL DE440s ephemeris)
