Chinese traditions / Calendar reference
Four Pillars Calculator: Stems, Branches and Solar Terms
Calculate traditional Four Pillars from a birth date, time and UTC offset. See elements, polarity, hidden stems, nayin and Ten Gods as structural reference labels.
Four Pillars Calculator: Stems, Branches and Solar Terms: The year changes at the instant of Start of Spring, and months at the twelve jie terms. Days follow a continuous sixty-day count anchored to 1949-10-01. Month and hour stems follow the Five Tigers and Five Rats rules. This is a cultural reference, without fortune-telling, compatibility readings or predictions. Runs 100% locally in your browser with zero server file uploads.
- Category
- Time & calendar tools
- Runs
- In your browser
- Cost
- Free · no sign-up
- Availability
- Ready to use
Runs entirely in your browser
A cultural reference to traditional rules; no fortune-telling, compatibility readings or predictions.
Use the UTC offset that applied at birth, including any daylight saving. Named time zones are not inferred. The supported dates are 1901–2099.
True solar time is off by default. When enabled, day and hour use local apparent solar time: clock time + 4 × longitude − UTC offset in minutes + the equation of time. At the date line, longitude is unwrapped to the zone’s nearest meridian. The equation of time uses NOAA’s approximation; a result near an hour or day boundary needs a more precise time check. Year and month still compare the actual instant with the solar terms.
In use: 00:00 day boundary. Late 子 zǐ (23:00–23:59) keeps the current day pillar, and its hour stem follows the next day (the 早子時/晚子時 convention); early 子 zǐ (00:00–00:59) uses the new day.
Civil clock: 1990-05-15 10:00:00; UTC offset: +08:00.
| Pillar | Stem and branch | 天干 tiān gān · Stem | 地支 dì zhī · Branch | 十神 shí shén · Ten Gods | 納音 nà yīn · Resonant element | 藏干 cáng gān · Hidden stems |
|---|---|---|---|---|---|---|
| Year | 庚午gēng wǔ | 庚 (gēng)金 jīn · Metal · 陽 yáng · Yang | 午 (wǔ)火 huǒ · Fire · 陽 yáng · Yang | 比肩 bǐ jiān · Peer | 路旁土 (lù páng tǔ)Roadside earth | 丁 (dīng) · 火 huǒ · Fire · 陰 yīn · Yin · 正官 zhèng guān · Direct officer己 (jǐ) · 土 tǔ · Earth · 陰 yīn · Yin · 正印 zhèng yìn · Direct resource |
| Month | 辛巳xīn sì | 辛 (xīn)金 jīn · Metal · 陰 yīn · Yin | 巳 (sì)火 huǒ · Fire · 陰 yīn · Yin | 劫財 jié cái · Rob wealth | 白蠟金 (bái là jīn)White-wax metal | 丙 (bǐng) · 火 huǒ · Fire · 陽 yáng · Yang · 七殺 qī shā · Seven killings戊 (wù) · 土 tǔ · Earth · 陽 yáng · Yang · 偏印 piān yìn · Indirect resource庚 (gēng) · 金 jīn · Metal · 陽 yáng · Yang · 比肩 bǐ jiān · Peer |
| Day | 庚辰gēng chén | 庚 (gēng)金 jīn · Metal · 陽 yáng · Yang | 辰 (chén)土 tǔ · Earth · 陽 yáng · Yang | 比肩 bǐ jiān · Peer日主 rì zhǔ · Day stem reference | 白蠟金 (bái là jīn)White-wax metal | 戊 (wù) · 土 tǔ · Earth · 陽 yáng · Yang · 偏印 piān yìn · Indirect resource乙 (yǐ) · 木 mù · Wood · 陰 yīn · Yin · 正財 zhèng cái · Direct wealth癸 (guǐ) · 水 shuǐ · Water · 陰 yīn · Yin · 傷官 shāng guān · Hurting officer |
| Hour | 辛巳xīn sì | 辛 (xīn)金 jīn · Metal · 陰 yīn · Yin | 巳 (sì)火 huǒ · Fire · 陰 yīn · Yin | 劫財 jié cái · Rob wealth | 白蠟金 (bái là jīn)White-wax metal | 丙 (bǐng) · 火 huǒ · Fire · 陽 yáng · Yang · 七殺 qī shā · Seven killings戊 (wù) · 土 tǔ · Earth · 陽 yáng · Yang · 偏印 piān yìn · Indirect resource庚 (gēng) · 金 jīn · Metal · 陽 yáng · Yang · 比肩 bǐ jiān · Peer |
Current 節 jié boundary: 立夏 lì xià · Start of summer, 1990-05-05 18:35:35 UTC. Next: 芒種 máng zhòng · Grain in ear, 1990-06-05 22:46:26 UTC.
Ten Gods are traditional relationship names, computed from the generating and controlling element cycles and matching or opposite polarity. They are labels only. Hidden stems are listed without strength weights. Luck pillars (大運 dà yùn) are outside this tool.
Rules and sources
The year changes at the exact 立春 lì chūn instant. Months change at the twelve 節 jié terms. The day count is anchored to 1949-10-01 = 甲子 jiǎ zǐ. Month and hour stems follow 五虎遁 wǔ hǔ dùn and 五鼠遁 wǔ shǔ dùn.
Day anchor: Purple Mountain Observatory, GB/T 33661-2017, and calc-site. Day-boundary conventions: Orphic Meridian. NOAA equation of time. URLs: https://www.pmo.cas.cn/xwdt2019/kpdt2019/202203/P020240201504886119982.pdf ; https://www.calc-site.com/search_dates/10/1/1949 ; https://www.orphicmeridian.com/en/library/zi-hour-day-boundary ; https://gml.noaa.gov/grad/solcalc/solareqns.PDF
Calendar boundaries and day anchor
The 24 solar-term instants reuse TOEA's solar-terms.ts. Year and month boundaries are astronomical instants, not whole Beijing dates. Purple Mountain Observatory's published calendar standard states 1949-10-01 is a Jia Zi day: https://www.pmo.cas.cn/xwdt2019/kpdt2019/202203/P020240201504886119982.pdf . A second published calendar confirms it: https://www.calc-site.com/search_dates/10/1/1949 . Day-boundary conventions: https://www.orphicmeridian.com/en/library/zi-hour-day-boundary
Traditional tables
Five Tigers and Five Rats: https://yiology.net/books/命/八字命理/懒人速查表/7 . Hidden stems table by Peter Yap: https://www.skillon.com/bazi-feng-shui.cfm/topic/2742/bazi-a-deeper-understanding-of-the-hidden-stems . Nayin's sixty combinations are stored as thirty adjacent pairs; complete sixty-combination table: https://www.divinehere.com/biginner/1003010.html ; classical names: https://zh.wikisource.org/wiki/三命通會/卷一 . The spelling variants and cross-checks are documented in NOTES. Ten Gods follow element generation/control and yin-yang polarity, with no interpretation.
Apparent solar clock
NOAA General Solar Position Calculations supplies the fractional-year equation-of-time approximation: https://gml.noaa.gov/grad/solcalc/solareqns.PDF . Longitude is east-positive. At the date line it is unwrapped to the meridian nearest the entered UTC offset, so the correction remains on the local civil-date branch. Solar-term comparisons never use this corrected clock.
How to use it
- Enter the birth date, local time and the UTC offset that applied then.
- Choose the midnight or 23:00 day boundary; optionally enable true solar time and enter a longitude.
- Read the four pillars and the current and next solar-term boundaries.
Privacy & limitations
All calculations run in your browser. Birth details are not uploaded or stored.
Related tools
Frequently asked questions
Does the year change at Lunar New Year?
No. Four Pillars uses the exact Start of Spring solar-term instant. The existing Chinese Zodiac Calculator uses Lunar New Year and serves a different calendar convention.
Which day boundary is the default?
Midnight, 00:00, in the early/late Zi hour convention (早子時/晚子時): between 23:00 and midnight the day pillar stays on the current day, while the hour stem follows the next day by the Five Rats rule. The 23:00 option instead advances the day pillar too, so both conventions give the same hour pillar.
What does true solar time change?
It changes the clock used for the day and hour by longitude and NOAA's approximate equation of time. Year and month continue to use the actual birth instant. The toggle is off by default. Near a clock boundary, the approximation and recorded birth-time precision matter.
How are time zones handled?
Enter an explicit UTC offset, including daylight saving if it applied. The default is +08:00. The tool does not infer historical offsets from a place name. Dates from 1901 to 2099 are supported.
Are luck pillars or readings included?
No. Elements, hidden stems, nayin and Ten Gods are displayed only as traditional classifications. Luck pillars, strength scores and interpretations are excluded.
Free tool · runs in your browser · no account required