The Nine Major Date Selection Systems (九大擇日體系)
Within the broad field of Ze Ri (擇日), nine major specialised systems have been developed over the centuries, each with its own methodology, primary tool, and optimal application domain. No single system covers all situations; professional practitioners select and combine systems based on the type of event, the parties involved, and the level of Feng Shui integration required.
System 1 — 12 Day Officers (十二建星 Shíèr Jiàn Xīng)
The most foundational system, forming the backbone of the popular Tong Shu almanac. The 12 Day Officers cycle through the 12 Earthly Branches in relation to the current month branch: Jian (建, Establish), Chu (除, Remove), Man (滿, Full), Ping (平, Balance), Ding (定, Stable), Zhi (執, Execute), Po (破, Break), Wei (危, Danger), Cheng (成, Success), Shou (收, Receive), Kai (開, Open), Bi (閉, Close).
Each Officer has specific auspicious and inauspicious activity associations. Cheng (成/Success) and Kai (開/Open) are generally most favourable; Po (破/Break) and Po (閉/Close) are generally least favourable. However, every officer has both suitable and unsuitable activities — even "Break" days can be used for activities involving removal, demolition, or ending.
System 2 — 28 Constellations (二十八星宿)
The most astronomically precise system for day selection, using the actual position of the Moon through the 28 Lunar Mansions (宿 Xiù). Each mansion has an inherent quality and specific activity associations. This system was historically used for imperial ceremonies and temple construction, and remains important for burial and geomancy-integrated date selection.
System 3 — Grandmaster Dong (董公擇日法)
Attributed to Dong Dezhang (董德彰) of the Tang Dynasty, this is the most widely used practical system for general-purpose events. It provides a pre-computed, month-by-month, day-by-day grading system based on the interaction between the current solar month and the day's Heavenly Stem-Earthly Branch combination. Each Jia Zi day within each solar month is assigned specific quality grades (Superior 上吉, Middle 次吉, Lower 可用, Inauspicious 不可用) and specific activity suitability lists (marriage, business opening, construction, travel, burial). See the dedicated Grandmaster Dong module for detailed coverage.
System 4 — Xuan Kong Da Gua (玄空大卦擇日法)
Uses the 64 hexagrams of the Yi Jing to align the selected date's hexagram energy with the building's sitting/facing hexagram energy in a Feng Shui context. The core concept is Yi Gua Chun Qing (一卦純清, One Gua Pure Clarity) — perfect harmonic alignment between time and space. This is the primary method for house moving, ground-breaking, and burial in Xuan Kong Feng Shui traditions. It requires knowledge of the building's orientation and the current Feng Shui period (currently Period 9: 2024–2043).
System 5 — Qi Men Dun Jia (奇門遁甲擇日法)
Uses the Qi Men Dun Jia cosmic board — with its Eight Gates (八門), Nine Stars (九星), and Eight Spirits (八神) — to find windows where the configuration aligns favourably for a specific action in a specific direction. Key gates for activities: Sheng (生/Life) for new beginnings; Kai (開/Open) for expansion and visibility; Xiu (休/Rest) for healing and relationships; Jing (景/View) for planning and strategy. This method provides direction-specific and action-type-specific precision unavailable in other systems.
System 6 — Great Sun Formula (太陽到山擇日法)
Based on the actual position of the Sun relative to the building or grave's sitting direction. The "Great Sun arrives at the Mountain" configuration occurs when the Sun transits the sector corresponding to the sitting direction — a powerful energetic activation moment. Particularly applicable for renovation, construction start, and geomantic activation. Not appropriate for selecting marriage dates.
System 7 — Great Moon Formula (太陰到山擇日法)
Analogous to the Great Sun formula but based on the Moon's position. The Moon's slower cycle (approximately 28 days per circuit) means "Great Moon at the Mountain" configurations occur about once per month for each direction. Particularly relevant for activities involving water, relationships, and yin (feminine, receptive) energies.
System 8 — San Qi Date Selection (三奇擇日法)
The San Qi (三奇, Three Marvels) are specific combinations of Heavenly Stems appearing in sequence: Tian Qi (天奇) = Jia, Wu, Geng; Di Qi (地奇) = Yi, Bing, Ding; Ren Qi (人奇) = Ren, Gui combined with Xin. When a day contains a San Qi configuration in the correct order across the Year-Month-Day-Hour pillars, it indicates extraordinary fortune. This system is used primarily for initiating ventures requiring exceptional talent recognition or academic achievement.
System 9 — Four Auspicious Stars (四大吉星擇日法)
Selects days when four specific auspicious stars align favourably relative to the individual or activity: Tian De (天德, Heavenly Virtue), Yue De (月德, Monthly Virtue), Tian Yi Gui Ren (天乙貴人, Heavenly Noble), and Hong Luan (紅鸞, Red Phoenix). When all four stars are present and active, the day carries exceptional protective and beneficent energy.
Choosing Between Systems by Activity
- Weddings: Grandmaster Dong + Tong Shu (12 Officers) + Personal BaZi of both parties
- Burial / Grave matters: XKDG + Great Sun + 28 Constellations
- Business Opening: Qi Men + Grandmaster Dong + Owner's BaZi
- House Moving: XKDG + Great Sun + Tong Shu
- Construction Start: Great Sun + Grandmaster Dong + XKDG
- Travel / Relocation: Tong Shu + Personal BaZi factors