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Tong Shu Calendar Reference

Auspicious Business Opening Dates for September 2026開業 · September 2026

By Master Sean Chan · Updated

This month carries Bai Lu (白露) — month flips to 酉 on September 7 (Singapore time): the BaZi calendar's sectional boundary for the month. Below is the universal Chinese metaphysics ranking of every day in September 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

30
days in September
26
pass hard requirements
5
rank as 上吉
5
top picks below
DateDay PillarOfficer 建除 Mansion 宿Clash 沖Class
12026-09-02壬午開 Opening翼子 (Rat)上吉
22026-09-25乙巳成 Completing井亥 (Pig)上吉
32026-09-10庚寅執 Holding箕申 (Monkey)上吉
42026-09-15乙未開 Opening危丑 (Ox)上吉
52026-09-27丁未開 Opening柳丑 (Ox)上吉

All days in September 2026

DateDay PillarOfficerMansion ClashNotable factorsClass
2026-09-01辛巳收張亥 Pig宿 張 · 黃道吉
2026-09-02壬午開翼子 Rat月德 · 建除 開上吉
2026-09-03癸未閉軫丑 Ox天德 · 建除 閉 · 宿 軫平
2026-09-04甲申建角寅 Tiger—平
2026-09-05乙酉除亢卯 Rabbit宿 亢平
2026-09-06丙戌滿氐辰 Dragon建除 滿 · 宿 氐 · 黃道吉
2026-09-07丁亥滿房巳 Snake建除 滿吉
2026-09-08戊子平心午 HorseFailed requirement: not_year_break大凶
2026-09-09己丑定尾未 Goat—平
2026-09-10庚寅執箕申 Monkey月德 · 建除 執 · 宿 箕上吉
2026-09-11辛卯破斗酉 RoosterFailed requirement: not_month_break大凶
2026-09-12壬辰危牛戌 Dog建除 危平
2026-09-13癸巳成女亥 Pig建除 成吉
2026-09-14甲午收虛子 Rat宿 虛 · 黃道平
2026-09-15乙未開危丑 Ox月德合 · 建除 開 · 宿 危上吉
2026-09-16丙申閉室寅 Tiger建除 閉凶
2026-09-17丁酉建壁卯 Rabbit黃道吉
2026-09-18戊戌除奎辰 Dragon—平
2026-09-19己亥滿婁巳 Snake建除 滿吉
2026-09-20庚子平胃午 HorseFailed requirement: not_year_break大凶
2026-09-21辛丑定昴未 Goat—平
2026-09-22壬寅執畢申 Monkey四離 · 建除 執 · 黃道凶
2026-09-23癸卯破觜酉 RoosterFailed requirement: not_month_break大凶
2026-09-24甲辰危參戌 Dog建除 危 · 宿 參平
2026-09-25乙巳成井亥 Pig月德合 · 建除 成 · 宿 井上吉
2026-09-26丙午收鬼子 Rat黃道吉
2026-09-27丁未開柳丑 Ox建除 開 · 黃道上吉
2026-09-28戊申閉星寅 Tiger建除 閉凶
2026-09-29己酉建張卯 Rabbit宿 張 · 黃道吉
2026-09-30庚戌除翼辰 Dragon月德吉
Personalised next step

BaZi-Aligned Date Report — September 2026

USD 388

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