Tong Shu Calendar Reference

Auspicious Business Opening Dates for May 2028開業 · May 2028

By Master Sean Chan · Updated April 27, 2026

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

days in May

pass hard requirements

rank as 上吉

top picks below

	Date	Day Pillar	Officer 建除	Mansion 宿	Clash 沖	Class
1	2028-05-27	乙卯	開 Opening	婁	酉 (Rooster)	上吉
2	2028-05-13	辛丑	成 Completing	亢	未 (Goat)	上吉
3	2028-05-07	乙未	滿 Filling	柳	丑 (Ox)	上吉
4	2028-05-18	丙午	除 Removing	箕	子 (Rat)	上吉
5	2028-05-19	丁未	滿 Filling	斗	丑 (Ox)	上吉

All days in May 2028

Date	Day Pillar	Officer	Mansion	Clash	Notable factors	Class
2028-05-01	己丑	收	昴	未 Goat	—	平
2028-05-02	庚寅	開	畢	申 Monkey	Failed 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 Snake	Failed 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 Monkey	Failed 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 Snake	Failed 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 Monkey	Failed 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

What this universal ranking cannot see

The above table reads the calendar in isolation. A complete date selection asks five further questions:

Personal day pillar clash. Your own day branch and your partner’s day branch each carry a 沖 (clash). A day that breaks either is unsafe for the two of you regardless of how it looks here.
Zodiac clash. Your year branch (zodiac) carries its own clash partner. A day clashing your year branch is reduced one full grade.
Useful god (用神). Each chart has elements it needs and elements it doesn’t. The day’s element either supports or undermines yours.
Hour selection. Within a chosen day, the right hour matters. Hours are deliberately not surfaced on this page — they are part of the personalised report.
Annual / monthly alignment. 2026 is a 丙午 (Yang Fire Horse) year. Whether your chart welcomes or fights the year shapes which days inside the year work best.

Combined, these can shift the ranking dramatically. The BaZi-Aligned Date Report below applies them.

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:

The single best day for you specifically in this month, plus two backups
For each, the auspicious 2-hour window (子丑寅卯辰巳午未申酉戌亥)
Any personal clash, 沖, or 害 hidden in the ranking above
Notes on what to do or avoid that day to compound the effect

Order the report →

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

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.

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.