Grandmaster Dong's Date Selection Method (董公擇日法)
The Dong Gong Ze Ri (董公擇日), attributed to Dong Dezhang (董德彰) of the Tang Dynasty, is the most widely used practical date selection system in the Chinese-speaking world. It forms the foundation of the popular Tong Shu almanac and is the primary reference for practitioners selecting dates for weddings, business openings, construction, and house moves. Its enduring popularity stems from its comprehensive coverage (every day of the year is graded), its specific activity recommendations, and its elegant integration of multiple classical factors into a single reference system.
Historical Background
Dong Dezhang served as an imperial astrologer during the Tang Dynasty and systematised an approach to date selection that could be applied by ordinary practitioners without requiring deep astronomical knowledge. His method encodes the accumulated wisdom of classical Chinese calendar science into a practical month-by-month, day-by-day reference that has been continuously updated and republished for over a thousand years. The system's longevity is testimony to its practical effectiveness.
The Three-Step Process
- Identify the Solar Month: Determine which of the 12 solar months (based on the 24 Solar Terms) contains the date in question. Solar months begin and end at the major solar term transitions (e.g., Month 1 = Li Chun to Jing Zhe).
- Obtain the Jia Zi (GanZhi combination): Identify the Heavenly Stem and Earthly Branch combination for the specific day — e.g., Ding You, Ren Chen, Jia Zi.
- Read the monthly chapter: Each of the 12 monthly chapters lists every possible Jia Zi day that can occur within that month, with commentary explaining: the day's quality grade (Superior/Middle/Lower/Inauspicious), what it is suitable for, what it must avoid, and the timeframe within which consequences will manifest (typically 60 days, 120 days, or 1–3 years).
Day Quality Grades
Grandmaster Dong classifies each day into four levels:
- Superior (上吉): Multiple auspicious stars present; beneficial for important activities including construction, marriage, business opening, house moving, burial. Consequences manifest as positive outcomes within 60–120 days or within the year.
- Middle / Next Best (次吉): Generally good quality with some cautions; suitable for most activities with awareness of the specific restrictions noted.
- Lower / Small Use (小用/可用): Marginal quality; acceptable for minor activities but not for major events.
- Inauspicious / Avoid (不可用/大凶): Multiple conflicting or killing stars; manifests as financial loss, injury, legal problems, or relationship difficulties within the stated timeframe.
Activity Categories Covered
Grandmaster Dong's system provides specific verdicts for the following activity types:
- Marriage and Betrothal (婚姻/納采): Including the announcement, the ceremony, and moving into the marital home.
- Business Opening (開張): The first day of operation for a new business.
- Construction and Renovation (起造/修造): Ground-breaking, setting the foundation stone (定磉), frame-raising (拴架), and major renovation.
- Moving House (入宅/移居): The date of moving possessions into a new residence.
- Travel and Official Appointments (出行/赴任): Beginning a journey or taking up a new position.
- Burial and Funeral (安葬/埋葬): The date of interment.
- Opening a New Field or Farm (田蚕/動土): Agricultural and soil-related activities.
The Interaction of Jia Zi and Solar Month
The most important insight of Grandmaster Dong's method is that the same Jia Zi day can have dramatically different quality in different solar months. For example, a day with the Heavenly Stem Bing and Earthly Branch Zi may be excellent in Month 4 (summer) but inauspicious in Month 11 (winter) due to the interaction between the day's elemental nature and the prevailing seasonal energy. The full system encodes 12 months × approximately 30 days × multiple possible Jia Zi = hundreds of specific verdicts.
Classical Caution on Context
The original text notes an important contextual principle (董公選擇日要覽): "For great and wealthy persons conducting important affairs, the rules differ from ordinary persons. Great and wealthy persons selecting a date need only an auspicious hour to establish the formation — even if the day itself has some inauspicious stars, these can be dissolved by the auspicious energy of the hour combined with the authority of the person. For ordinary people, the same day may bring difficulty. Therefore, selecting a date requires consulting both the calendar and the individual's birth information (本命)."
Integration with Other Systems
In modern professional practice, Grandmaster Dong is used as the third filter layer after eliminating breaker days (Layer 1) and checking the 12 Day Officers (Layer 2). The Dong Gong verdict narrows the field of acceptable days significantly. The remaining candidates are then cross-checked against the individual's personal BaZi (Layer 4) and, where Feng Shui integration is needed, against XKDG or Great Sun formulas (Layer 5).