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Tong Shu Calendar Reference

Auspicious Business Opening Dates for September 2027開業 · September 2027

By Master Sean Chan · Updated

This month carries Bai Lu (白露) — month flips to 酉 on September 8 (Singapore time): the BaZi calendar's sectional boundary for the month. Below is the universal Chinese metaphysics ranking of every day in September 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

30
days in September
24
pass hard requirements
2
rank as 上吉
5
top picks below
DateDay PillarOfficer 建除 Mansion 宿Clash 沖Class
12027-09-10乙未Opening丑 (Ox)上吉
22027-09-20乙巳Completing亥 (Pig)上吉
32027-09-03戊子Stabilising午 (Horse)
42027-09-25庚戌Removing辰 (Dragon)
52027-09-01丙戌滿 Filling辰 (Dragon)

All days in September 2027

DateDay PillarOfficerMansion ClashNotable factorsClass
2027-09-01丙戌滿辰 Dragon建除 滿 · 黃道
2027-09-02丁亥巳 Snake月德合 · 建除 平 · 宿 軫
2027-09-03戊子午 Horse天德合 · 黃道
2027-09-04己丑未 GoatFailed requirement: not_year_break大凶
2027-09-05庚寅申 MonkeyFailed requirement: not_month_break大凶
2027-09-06辛卯酉 Rooster建除 危
2027-09-07壬辰戌 Dog建除 危
2027-09-08癸巳亥 Pig建除 成
2027-09-09甲午子 Rat宿 箕 · 黃道
2027-09-10乙未丑 Ox月德合 · 建除 開 · 宿 斗上吉
2027-09-11丙申寅 Tiger建除 閉
2027-09-12丁酉卯 Rabbit黃道
2027-09-13戊戌辰 Dragon宿 虛
2027-09-14己亥滿巳 Snake建除 滿 · 宿 危
2027-09-15庚子午 Horse月德 · 建除 平 · 黃道
2027-09-16辛丑未 GoatFailed requirement: not_year_break大凶
2027-09-17壬寅申 Monkey建除 執 · 黃道
2027-09-18癸卯酉 RoosterFailed requirement: not_month_break大凶
2027-09-19甲辰戌 Dog建除 危
2027-09-20乙巳亥 Pig月德合 · 建除 成上吉
2027-09-21丙午子 Rat黃道
2027-09-22丁未丑 Ox四離 · 建除 開 · 黃道
2027-09-23戊申寅 Tiger建除 閉 · 宿 參
2027-09-24己酉卯 Rabbit宿 井 · 黃道
2027-09-25庚戌辰 Dragon月德
2027-09-26辛亥滿巳 Snake建除 滿
2027-09-27壬子午 Horse建除 平 · 黃道
2027-09-28癸丑未 GoatFailed requirement: not_year_break大凶
2027-09-29甲寅申 Monkey建除 執 · 黃道
2027-09-30乙卯酉 RoosterFailed requirement: not_month_break大凶
Personalised next step

BaZi-Aligned Date Report — September 2027

USD 388

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

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.