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Tong Shu Calendar Reference

Auspicious Business Opening Dates for May 2028開業 · May 2028

By Master Sean Chan · Updated

This month carries Li Xia (立夏) — start of the BaZi summer on May 5 (Singapore time): the BaZi calendar's sectional boundary for the month. Mid-month transition into the BaZi summer; element balance shifts noticeably across the term.Below is the universal Chinese metaphysics ranking of every day in May 2028 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 May
26
pass hard requirements
6
rank as 上吉
5
top picks below
DateDay PillarOfficer 建除 Mansion 宿Clash 沖Class
12028-05-27乙卯開 Opening婁酉 (Rooster)上吉
22028-05-13辛丑成 Completing亢未 (Goat)上吉
32028-05-07乙未滿 Filling柳丑 (Ox)上吉
42028-05-18丙午除 Removing箕子 (Rat)上吉
52028-05-19丁未滿 Filling斗丑 (Ox)上吉

All days in May 2028

DateDay PillarOfficerMansion ClashNotable factorsClass
2028-05-01己丑收昴未 Goat—平
2028-05-02庚寅開畢申 MonkeyFailed requirement: not_year_break大凶
2028-05-03辛卯閉觜酉 Rooster建除 閉凶
2028-05-04壬辰閉參戌 Dog四絕 · 建除 閉 · 宿 參大凶
2028-05-05癸巳建井亥 Pig宿 井吉
2028-05-06甲午除鬼子 Rat黃道吉
2028-05-07乙未滿柳丑 Ox月德合 · 建除 滿 · 黃道上吉
2028-05-08丙申平星寅 Tiger天德合 · 建除 平吉
2028-05-09丁酉定張卯 Rabbit宿 張吉
2028-05-10戊戌執翼辰 Dragon建除 執 · 黃道吉
2028-05-11己亥破軫巳 SnakeFailed requirement: not_month_break大凶
2028-05-12庚子危角午 Horse月德 · 建除 危吉
2028-05-13辛丑成亢未 Goat天德 · 建除 成 · 宿 亢上吉
2028-05-14壬寅收氐申 MonkeyFailed requirement: not_year_break大凶
2028-05-15癸卯開房酉 Rooster建除 開吉
2028-05-16甲辰閉心戌 Dog建除 閉 · 黃道凶
2028-05-17乙巳建尾亥 Pig月德合吉
2028-05-18丙午除箕子 Rat天德合 · 宿 箕 · 黃道上吉
2028-05-19丁未滿斗丑 Ox建除 滿 · 宿 斗 · 黃道上吉
2028-05-20戊申平牛寅 Tiger建除 平平
2028-05-21己酉定女卯 Rabbit—平
2028-05-22庚戌執虛辰 Dragon月德 · 建除 執 · 宿 虛上吉
2028-05-23辛亥破危巳 SnakeFailed requirement: not_month_break大凶
2028-05-24壬子危室午 Horse建除 危平
2028-05-25癸丑成壁未 Goat建除 成 · 黃道吉
2028-05-26甲寅收奎申 MonkeyFailed requirement: not_year_break大凶
2028-05-27乙卯開婁酉 Rooster月德合 · 建除 開上吉
2028-05-28丙辰閉胃戌 Dog天德合 · 建除 閉 · 黃道平
2028-05-29丁巳建昴亥 Pig—平
2028-05-30戊午除畢子 Rat黃道吉
2028-05-31己未滿觜丑 Ox建除 滿 · 黃道吉
Personalised next step

BaZi-Aligned Date Report — May 2028

USD 388

A personalised PDF that re-ranks every business opening-suitable day in May 2028 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.