How Qimena Casts a Qi Men Chart: Rules, Worked Example and Verification

A Qimena chart is not “generated”; it is calculated by fixed rules, step by step, so the same time and place always give the same chart. This page publishes each rule, a worked example you can check by hand, and how our results compare with authoritative data, so you can check us.

What we checked

Item	How it was checked	Result
Solar-term instants	All 72 terms in 2026–2028 compared with the Hong Kong Observatory’s published times	All within 15 minutes; largest 14.1 min, average 4.6 min; 66 within 10 min
Day pillar	73,414 days from 1900 to 2100 compared with an independent Julian Day formula, in 5 time zones; plus 1949-10-01 (Jia Zi) and 2000-01-01 (Wu Wu)	Zero mismatches
Ju table	The 72 ju numbers (24 terms × three yuan) reviewed line by line against the traditional mnemonic table	Match
Full chart vs independent software	Not yet done systematically	Pending; results will be published

The rules, step by step

1. Fix the time. Take the exact moment of casting and convert it to the True Solar Time of the place: True Solar Time = the moment + the longitude offset + the equation of time, where the longitude offset is “longitude × 4 minutes − the time zone offset” and the equation of time comes from a standard approximation for that date (how it works). The time zone and daylight saving time come from the zone’s rules, so you never convert to Beijing time.
2. Four pillars. The year and month pillars come from the sun’s ecliptic longitude at the absolute moment: the year changes at Li Chun (longitude 315°), each month spans 30° from Li Chun, and the month stem follows the Five Tigers rule. The day and hour pillars use True Solar Time: the day pillar follows the continuous 60-day cycle (anchored on 2000-01-01, a Wu Wu day) and changes at 23:00 True Solar Time (the whole Zi hour belongs to the next day); the hour pillar is one of twelve two-hour periods (23:00–01:00 is Zi), with the stem from the Five Rats rule.
3. Solar term and ju (Chai Bu). The sun’s longitude divides the year into 24 solar terms of 15° each. From Winter Solstice through Grain in Ear (12 terms) the chart is Yang Dun; from Summer Solstice through Major Snow it is Yin Dun. The yuan (upper, middle, lower) comes from the branch of the day’s leading Jia or Ji day: Zi, Wu, Mao, You are upper; Yin, Shen, Si, Hai middle; Chen, Xu, Chou, Wei lower. The ju number then comes from the traditional table by “solar term × yuan.”
4. Earth Plate. Place Wu, Ji, Geng, Xin, Ren, Gui, Ding, Bing, Yi in order through the nine palaces starting at the ju’s palace: forward through the palace numbers in Yang Dun, backward in Yin Dun.
5. Xun head, Chief Star and Chief Door. The hour pillar’s decade (Jia Zi, Jia Xu, Jia Shen, Jia Wu, Jia Chen, Jia Yin) sets the xun head, whose Jia hides beneath Wu, Ji, Geng, Xin, Ren or Gui. The palace where that hidden stem sits on the Earth Plate gives its home star as the Chief Star and its home door as the Chief Door.
6. Heaven Plate (nine stars, rotating plate). The stars turn as one ring so the Chief Star lands on the palace of the hour stem on the Earth Plate (the hidden stem if the hour stem is Jia); each star carries the Earth stem of its home palace with it.
7. Human Plate (eight doors). The Chief Door starts at the xun head’s palace and walks through palaces 1 to 9, forward in Yang Dun and backward in Yin Dun, as many steps as the hour is from the xun head; the doors turn as one ring so the Chief Door lands there.
8. Spirit Plate (eight deities). The Chief deity sits with the Chief Star, and the other seven follow around the eight palaces: clockwise in Yang Dun and counterclockwise in Yin Dun.
9. Center palace. No star or door is placed there of its own; Tian Qin lodges in Kun 2. When the xun head falls in the center, the Chief Star is recorded as Tian Qin and the Chief Door as the Death Door, and the chart is laid out from Kun 2.
10. Voids, strength and patterns. Mark the palaces of the two void branches of the decade; mark each palace prosperous, assisting, resting, confined or dead by the season of the month branch; and detect patterns such as the Five Non-Encounters Hour, Fu Yin and Fan Yin (pattern glossary).

Worked example: 6 February 2027, 10:00 a.m., Shanghai (121.47° E)

Step 1, time. Shanghai time 10:00, longitude offset +5.9 minutes and equation of time about −14.3 minutes, so True Solar Time is about 09:51.

Step 2, four pillars. Li Chun arrived on 4 February 2027 at 09:46 Hong Kong time, so the year pillar is Ding Wei. It is a Yin (tiger) month, and a Ding year starts its months on Ren, so the month pillar is Ren Yin. The day pillar is Bing Chen. True Solar Time 09:51 is the Si hour, and on a Bing day the Si hour is Gui Si.

Step 3, ju. The sun’s longitude is about 317°, in the Start of Spring term, so it is Yang Dun. The leading day of Bing Chen is Jia Yin, and Yin belongs to the middle yuan. The Start of Spring row reads 8, 5, 2, and the middle yuan takes 5: Yang Dun ju 5.

Step 4, Earth Plate. Starting at palace 5 and going forward: Wu 5, Ji 6, Geng 7, Xin 8, Ren 9, Gui 1, Ding 2, Bing 3, Yi 4.

Step 5, Chief Star and Chief Door. Gui Si belongs to the Jia Shen decade, whose head Jia Shen hides beneath Geng. Geng sits in palace 7 (Dui), so the Chief Star is Dui’s home star, Tian Zhu, and the Chief Door is Dui’s home door, the Fright Door.

Step 6, Heaven Plate. The hour stem Gui sits in palace 1 (Kan) on the Earth Plate, so the Chief Star Tian Zhu turns to Kan 1, carrying Geng, the Earth stem of its home palace, Dui 7.

Step 7, Human Plate. Gui Si is nine hours after Jia Shen, so the Chief Door walks nine steps from palace 7 and comes all the way around to palace 7: the Fright Door stays in Dui 7.

Step 8, Spirit Plate. The Chief deity sits with Tian Zhu in Kan 1 and the others follow clockwise: Soaring Serpent in Gen 8, Great Yin in Zhen 3, Six Harmony in Xun 4, White Tiger in Li 9, Black Tortoise in Kun 2, Nine Earth in Dui 7 and Nine Heaven in Qian 6.

Step 9, voids. The Jia Shen decade’s void branches are Wu and Wei, which fall in Li 9 and Kun 2.

The board our engine produces matches this derivation exactly:

Xun 4	Li 9 (void)	Kun 2 (void)
Heaven Xin / Earth Yi Tian Ren · Block Door · Six Harmony	Heaven Bing / Earth Ren Tian Chong · Scenery Door · White Tiger	Heaven Yi / Earth Ding Tian Fu · Death Door · Black Tortoise
Zhen 3	Center 5	Dui 7
Heaven Gui / Earth Bing Tian Peng · Harm Door · Great Yin	Earth Wu (Tian Qin lodges in Kun 2)	Heaven Ren / Earth Geng Tian Ying · Fright Door · Nine Earth
Gen 8	Kan 1	Qian 6
Heaven Ji / Earth Xin Tian Xin · Life Door · Soaring Serpent	Heaven Geng / Earth Gui Tian Zhu · Rest Door · Chief	Heaven Ding / Earth Ji Tian Rui · Open Door · Nine Heaven

No whole-chart or palace-level pattern is triggered for this chart.

Our solar terms against the Hong Kong Observatory (2027)

The Hong Kong Observatory publishes exact solar-term instants each year, based on data from HM Nautical Almanac Office and the US Naval Observatory. The table compares its 2027 times with the instants our engine computes (a positive difference means our engine is later):

Solar term	HKO official (HKT)	Qimena engine (HKT)	Difference (min)
Minor Cold (小寒)	1/5 22:10	1/5 22:11	+1.3
Major Cold (大寒)	1/20 15:30	1/20 15:33	+3.5
Start of Spring (立春)	2/4 09:46	2/4 09:47	+1.4
Rain Water (雨水)	2/19 05:33	2/19 05:36	+4.0
Awakening of Insects (惊蛰)	3/6 03:40	3/6 03:40	+0.2
Spring Equinox (春分)	3/21 04:25	3/21 04:27	+2.2
Clear and Bright (清明)	4/5 08:17	4/5 08:17	+0.7
Grain Rain (谷雨)	4/20 15:18	4/20 15:19	+1.2
Start of Summer (立夏)	5/6 01:25	5/6 01:26	+1.1
Grain Buds (小满)	5/21 14:18	5/21 14:19	+1.6
Grain in Ear (芒种)	6/6 05:26	6/6 05:28	+2.6
Summer Solstice (夏至)	6/21 22:11	6/21 22:12	+1.1
Minor Heat (小暑)	7/7 15:37	7/7 15:41	+4.7
Major Heat (大暑)	7/23 09:05	7/23 09:05	+0.8
Start of Autumn (立秋)	8/8 01:27	8/8 01:33	+6.1
End of Heat (处暑)	8/23 16:14	8/23 16:16	+2.4
White Dew (白露)	9/8 04:28	9/8 04:36	+8.7
Autumn Equinox (秋分)	9/23 14:02	9/23 14:05	+3.3
Cold Dew (寒露)	10/8 20:17	10/8 20:26	+9.2
Frost’s Descent (霜降)	10/23 23:33	10/23 23:36	+3.6
Start of Winter (立冬)	11/7 23:39	11/7 23:46	+7.8
Minor Snow (小雪)	11/22 21:16	11/22 21:18	+2.7
Major Snow (大雪)	12/7 16:38	12/7 16:44	+6.5
Winter Solstice (冬至)	12/22 10:42	12/22 10:43	+1.7

Across all 72 terms in 2026–2028: largest gap 14.1 minutes, average absolute gap 4.6 minutes, average signed gap +2.4 minutes (the engine runs slightly late). The Li Chun gaps for the three years, in minutes, are 2026: -4.0, 2027: +1.4, 2028: +5.9. Source: Hong Kong Observatory.

Conventions and known limits

• Solar terms are accurate to about 15 minutes. The engine uses a standard low-precision solar position formula, and every term is within 15 minutes of the Hong Kong Observatory. If you cast within 15 minutes of a boundary, the year pillar, month pillar and ju number may sit on the other side from a minute-exact almanac.
• The day changes at 23:00 True Solar Time (Zi-start day change). The whole Zi hour (23:00–01:00) belongs to the next day, and both the day pillar and the hour stem come from that day. This is the mainstream practice in BaZi and Qi Men software today; a second school, the “night Zi hour does not change the day” school, changes the day at 00:00, so its charts for the late Zi hour (23:00–24:00) will differ from ours. In the birth-chart hour picker, Zi is read as 00:00–01:00 of the chosen date, so for someone born after 23:00, enter the next day’s date.
• Longitude only, not latitude. The place sets True Solar Time through its longitude.
• Birth times are not converted automatically. The automatic handling of True Solar Time and DST applies to charts cast for now or for a chosen time; convert a birth time by hand first (how to convert it).
• School. Chai Bu to set the ju and the rotating plate to lay out the chart (why we chose them). Software using Zhi Run or the flying plate will give different charts, and that does not mean either one is wrong.

Corrections log

• 2026-09-29: The day pillar now changes at 23:00 True Solar Time (Zi-start day change) instead of 00:00, so the late Zi hour no longer takes the same day’s pillar and stem.
• 2026-09-29: Fu Yin and Fan Yin used to test only the doors; both the stars and the doors must now match. Over the 4,380 two-hour charts of 2027, Fu Yin flags fell from 973 to 543 and Fan Yin flags from 488 to 83.
• 2026-09-25: The birth-chart year pillar now changes at Li Chun, and a bug that read birth dates as the previous day for users in the Americas was fixed.

Want to check for yourself?

In the free AI charting tool, choose “Choose date & time,” enter the time and place of the example above, and compare the board with this page. If another tool gives you a different result, send us the software name, time, place and the difference at [email protected]; we will check each one and add the outcome to this page.