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Tong Shu Calendar Reference

Auspicious Business Opening Dates for December 2027開業 · December 2027

By Master Sean Chan · Updated

This month carries Da Xue (大雪) — month flips to 子 on December 7 (Singapore time): the BaZi calendar's sectional boundary for the month. Winter solstice (冬至) lands within this month — the year's lowest Yang point, commonly avoided for major ceremonial events.Below is the universal Chinese metaphysics ranking of every day in December 2027 for opening a business (開市), derived from the classical Tong Shu (通書). Opening is treated as a 'beginning' — the rules favour 開 (Opening) and 建 (Establishing) officers and Yellow Dao days carrying 天德 / 月德 protection.

Top-ranked dates this month

31
days in December
26
pass hard requirements
3
rank as 上吉
5
top picks below
DateDay PillarOfficer 建除 Mansion 宿Clash 沖Class
12027-12-16壬申成 Completing參寅 (Tiger)上吉
22027-12-03己未成 Completing斗丑 (Ox)上吉
32027-12-30丙戌開 Opening箕辰 (Dragon)上吉
42027-12-28甲申成 Completing心寅 (Tiger)吉
52027-12-05辛酉開 Opening女卯 (Rabbit)吉

All days in December 2027

DateDay PillarOfficerMansion ClashNotable factorsClass
2027-12-01丁巳破尾亥 PigFailed requirement: not_month_break大凶
2027-12-02戊午危箕子 Rat建除 危 · 宿 箕 · 黃道平
2027-12-03己未成斗丑 Ox月德合 · 建除 成 · 宿 斗上吉
2027-12-04庚申收牛寅 Tiger天德合吉
2027-12-05辛酉開女卯 Rabbit建除 開吉
2027-12-06壬戌閉虛辰 Dragon建除 閉 · 宿 虛 · 黃道凶
2027-12-07癸亥閉危巳 Snake建除 閉 · 宿 危大凶
2027-12-08甲子建室午 Horse黃道吉
2027-12-09乙丑除壁未 GoatFailed requirement: not_year_break大凶
2027-12-10丙寅滿奎申 Monkey建除 滿吉
2027-12-11丁卯平婁酉 Rooster月德合 · 建除 平 · 黃道吉
2027-12-12戊辰定胃戌 Dog—平
2027-12-13己巳執昴亥 Pig建除 執吉
2027-12-14庚午破畢子 RatFailed requirement: not_month_break大凶
2027-12-15辛未危觜丑 Ox建除 危平
2027-12-16壬申成參寅 Tiger月德 · 建除 成 · 宿 參上吉
2027-12-17癸酉收井卯 Rabbit宿 井 · 黃道吉
2027-12-18甲戌開鬼辰 Dragon建除 開吉
2027-12-19乙亥閉柳巳 Snake建除 閉凶
2027-12-20丙子建星午 Horse黃道吉
2027-12-21丁丑除張未 GoatFailed requirement: not_year_break大凶
2027-12-22戊寅滿翼申 Monkey建除 滿吉
2027-12-23己卯平軫酉 Rooster建除 平 · 宿 軫 · 黃道平
2027-12-24庚辰定角戌 Dog—平
2027-12-25辛巳執亢亥 Pig建除 執 · 宿 亢平
2027-12-26壬午破氐子 RatFailed requirement: not_month_break大凶
2027-12-27癸未危房丑 Ox建除 危平
2027-12-28甲申成心寅 Tiger建除 成 · 黃道吉
2027-12-29乙酉收尾卯 Rabbit黃道吉
2027-12-30丙戌開箕辰 Dragon建除 開 · 宿 箕上吉
2027-12-31丁亥閉斗巳 Snake月德合 · 建除 閉 · 宿 斗平
Personalised next step

BaZi-Aligned Date Report — December 2027

USD 388

A personalised PDF that re-ranks every business opening-suitable day in December 2027 against your BaZi (and, for weddings/ROM, your partner’s BaZi). It surfaces:

Order the report →

See the full glossary of classical date-selection terms in the BaZi Glossary & Auxiliary Stars.

Further reading from the blog

Selected posts from Master Sean Chan's blog covering this topic and closely related ones in practice:

Frequently asked

Why isn’t my day on the list of top 5?

The top list is the universal ranking before any personal adjustment. Many couples find their best date isn’t in the top 5. Once you account for your day pillars, the right day often shifts. That’s exactly the gap the BaZi-Aligned Date Report fills.

What does 大凶 mean and can it ever be overridden?

大凶 means the day fails a hard classical requirement: 月破 (month break), 歲破 (year break), or 四離/四絕 (a quarter-day boundary). These cannot be overridden by personal alignment; they are excluded categorically. Choose another day.

Why don’t you show times here?

Hour selection is personal. The right hour depends on your day pillar and the chosen day’s element relationship to it. Publishing universal “auspicious hours” misleads readers into thinking a generic hour is safe; it isn’t. Hours are included in the personalised report.

Where do these scores come from?

The classical Tong Shu (通書) tradition: 建除十二神 (Twelve Officers), 二十八宿 (Twenty-Eight Mansions), 月德 / 天德 (monthly and yearly virtue stars), 黃黑道 (Yellow/Black Dao), and the Dong Gong (董公) per-purpose rules. We compute these directly from astronomical solar terms — no app shortcuts.

Should I open the business on the same day as my company registration?

If you can — yes. Aligning the opening with the legal incorporation compounds the day’s influence on both events. If they have to be different, prioritise the opening (the customer-facing first day) over the registration date.

Methodology

Day pillars derive from the standard 60 Jiazi anchor (sexagenary day cycle, anchored against the published Tong Shu). Year pillars switch on Li Chun (立春), the first solar term of the BaZi year, computed from the truncated VSOP87 series for solar longitude. Month pillars switch on each sectional solar term. The Twelve Officers are the day branch’s offset from the month branch; the Twenty-Eight Mansions cycle every 28 days against an authoritative anchor.

Per-purpose rules follow the Dong Gong (董公擇日) tradition with adjustments encoded in our open purpose_rules.yaml. Scores are additive over the day’s present 神煞, the officer/mansion preference, and the Yellow Dao bonus, then clamped to 0–100 and classified.