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Tong Shu Calendar Reference

Auspicious Business Opening Dates for December 2026開業 · December 2026

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 2026 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
24
pass hard requirements
2
rank as 上吉
5
top picks below
DateDay PillarOfficer 建除 Mansion 宿Clash 沖Class
12026-12-11壬戌開 Opening奎辰 (Dragon)上吉
22026-12-04乙卯定 Stabilising斗酉 (Rooster)上吉
32026-12-09庚申成 Completing室寅 (Tiger)吉
42026-12-23甲戌開 Opening翼辰 (Dragon)吉
52026-12-02癸丑滿 Filling尾未 (Goat)吉

All days in December 2026

DateDay PillarOfficerMansion ClashNotable factorsClass
2026-12-01壬子除心午 HorseFailed requirement: not_year_break大凶
2026-12-02癸丑滿尾未 Goat建除 滿 · 黃道吉
2026-12-03甲寅平箕申 Monkey月德 · 建除 平 · 宿 箕吉
2026-12-04乙卯定斗酉 Rooster天德 · 宿 斗上吉
2026-12-05丙辰執牛戌 Dog建除 執 · 黃道吉
2026-12-06丁巳破女亥 PigFailed requirement: not_month_break大凶
2026-12-07戊午破虛子 RatFailed requirement: not_month_break大凶
2026-12-08己未危危丑 Ox建除 危 · 宿 危凶
2026-12-09庚申成室寅 Tiger建除 成 · 黃道吉
2026-12-10辛酉收壁卯 Rabbit黃道吉
2026-12-11壬戌開奎辰 Dragon月德 · 建除 開上吉
2026-12-12癸亥閉婁巳 Snake建除 閉凶
2026-12-13甲子建胃午 HorseFailed requirement: not_year_break大凶
2026-12-14乙丑除昴未 Goat黃道吉
2026-12-15丙寅滿畢申 Monkey建除 滿吉
2026-12-16丁卯平觜酉 Rooster月德合 · 建除 平 · 黃道吉
2026-12-17戊辰定參戌 Dog宿 參吉
2026-12-18己巳執井亥 Pig建除 執 · 宿 井吉
2026-12-19庚午破鬼子 RatFailed requirement: not_month_break大凶
2026-12-20辛未危柳丑 Ox建除 危平
2026-12-21壬申成星寅 Tiger月德 · 四離 · 建除 成吉
2026-12-22癸酉收張卯 Rabbit宿 張 · 黃道吉
2026-12-23甲戌開翼辰 Dragon建除 開吉
2026-12-24乙亥閉軫巳 Snake建除 閉 · 宿 軫凶
2026-12-25丙子建角午 HorseFailed requirement: not_year_break大凶
2026-12-26丁丑除亢未 Goat月德合 · 宿 亢 · 黃道吉
2026-12-27戊寅滿氐申 Monkey建除 滿 · 宿 氐吉
2026-12-28己卯平房酉 Rooster建除 平 · 黃道平
2026-12-29庚辰定心戌 Dog—平
2026-12-30辛巳執尾亥 Pig建除 執吉
2026-12-31壬午破箕子 RatFailed requirement: not_month_break大凶
Personalised next step

BaZi-Aligned Date Report — December 2026

USD 388

A personalised PDF that re-ranks every business opening-suitable day in December 2026 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

Each day’s pillar is computed from the 60 Jiazi rotation anchored against the published Tong Shu, not from any single calendar app. The BaZi year flips at Li Chun (立春) and the BaZi month flips at every sectional solar term, both calculated from VSOP87 solar-longitude data so the boundaries land on the right minute. Twelve Officers and the 28 Mansions each rotate deterministically against well-known anchors.

The per-purpose weights are Dong Gong’s (董公擇日) — adjusted where modern almanacs disagree, in favour of the Hong Kong Observatory and Taiwan CWB lineage. Auspicious stars add to the score, taboo stars subtract, the day’s officer and mansion shift it further, and Yellow Dao adds a final small bonus. The final number gets capped at 100 and mapped to one of five tiers.