BaZi calculator: your Four Pillars, with every step shown

The year is 庚午 because the birth came after Lichun 1990 (Feb 4, 1990, 10:14 China Standard Time). The month is 辛巳: the Snake month began at Start of Summer (立夏) on May 6, 1990 at 02:35 China Standard Time. The day 丁丑 makes Ding Fire (丁) the Day Master, and 08:30 falls in the Dragon hour (07:00 to 09:00), whose stem on a Ding day is Jia, giving 甲辰.

1. Year pillar: the solar year starts at Lichun (立春), not on January 1 or at Chinese New Year. The stem and branch follow the 60-year cycle; 2026 is 丙午 (Bing Wu) from Lichun on Feb 4, 2026.
2. Month pillar: each month starts at one of the twelve "jie" solar terms and always has the same branch. Its stem follows the year stem (甲 and 己 years start with 丙寅, 乙 and 庚 with 戊寅, 丙 and 辛 with 庚寅, 丁 and 壬 with 壬寅, 戊 and 癸 with 甲寅).
3. Day pillar: the 60-day cycle has run without a break for more than two thousand years. Today, Oct 20, 2026, is 丁卯 (Ding Mao).
4. Hour pillar: twelve two-hour periods from the Zi hour (23:00 to 01:00). The stem follows the day stem (甲 and 己 days start with 甲子, 乙 and 庚 with 丙子, 丙 and 辛 with 戊子, 丁 and 壬 with 庚子, 戊 and 癸 with 壬子).

• 甲 Jia Wood
  the wood of root and trunk
• 乙 Yi Wood
  the wood of branches and leaves
• 丙 Bing Fire
  blazing, burning fire
• 丁 Ding Fire
  warm, gentle fire
• 戊 Wu Earth
  the earth of hills and ridges
• 己 Ji Earth
  the earth of fields and gardens
• 庚 Geng Metal
  yang metal, the essence of Venus
• 辛 Xin Metal
  yin metal: not jewels or jade, simply warm, soft, clear and moist
• 壬 Ren Water
  the source of Gui water, which is both the hundred rivers and the rain and dew
• 癸 Gui Water
  pure yin and the weakest stem

Elements produce each other in the order Wood, Fire, Earth, Metal, Water, and control each other in the order Wood, Earth, Water, Fire, Metal. Seven Killings (七杀) is also called Pian Guan (偏官).

• Year boundary: Lichun is the BaZi year boundary. Calculators that use Chinese New Year give births between Chinese New Year and Lichun the wrong year pillar.
• Exact solar-term time: the month changes at an instant. Births within minutes of a solar term depend on the exact time; our solar-term times agree with sxtwl to within 2 minutes.
• Time zone and daylight saving: a solar term is one instant worldwide, so births outside China are converted to UTC first. Summer time (China used it from 1986 to 1991) shifts the clock by an hour.
• Clock time or solar time: some practitioners convert to apparent solar time from the birthplace longitude. In far-western China it can reach nearly three hours (Kashgar lies about 44 degrees west of the 120°E meridian of China Standard Time).
• Day boundary and rounding: calculators differ on whether the day starts at 23:00 or midnight, and on how they round the luck-pillar starting age.

• 66,240 four-pillar results compared with lunar-javascript (6tail), under both day rules, including every solar term one minute before and after and every 23:00 and midnight edge: 0 differences. Luck pillars and starting ages: 3,000 checks, 0 differences.
• 2,412 solar-term moments compared with sxtwl (寿星天文历): largest difference 2 minutes. Year, month and day pillars for 72,564 days, March 1901 to October 2099: 2 differences, on the two dates in 1917 and 1927 where a solar term falls within minutes of midnight: sxtwl and the Hong Kong Observatory table put it on the other side of midnight from our engine. The calculator flags births near those two moments.
• The solar-term data is the same set we check day by day against the Hong Kong Observatory tables; see how we check the dates.

• 淵海子平 (Yuan Hai Zi Ping) on Chinese Wikisource
• 滴天髓 (Di Tian Sui), 天干論, on Chinese Wikisource
• 三命通會 (San Ming Tong Hui) on Chinese Wikisource
• 淮南子 (Huainanzi), 天文訓, on Chinese Wikisource
• Stanford Encyclopedia of Philosophy: Chinese Metaphysics
• Internet Encyclopedia of Philosophy: Yinyang
• Hong Kong Observatory, Gregorian-Lunar Calendar Conversion Table