Chinese Wedding Dates: How the Almanac Actually Works.
Chinese date selection is the most elaborate system in this list, and the part everyone skips is that two reputable automated almanacs will give you opposite answers for the same day.
The calendar
Lunisolar, standardised as GB/T 33661-2017 and computed by the Purple Mountain Observatory. New moons and solar terms are calculated at 120°E, Beijing time, which is why the Vietnamese calendar at UTC+7 and the Korean at UTC+9 occasionally diverge by a day.
The rules
- The twelve Day Officers (建除十二神)
- Each day carries one of twelve officers, assigned from the day's earthly branch relative to the solar-term month. Sources agree that 建, 破, 平, 收 and 闭 are unfavourable and 成 is good; they disagree about 满, 危 and 开.
- Yellow path and black path (黄道黑道)
- A separate twelve-god cycle whose starting point depends on the month. Six gods are auspicious, six are not.
- The 28 mansions (二十八宿)
- A fixed 28-day cycle. Roughly half favour marriage. Note that almanacs disagree about the epoch by several days.
- Zodiac clash (冲)
- Each day clashes with the opposite branch, and therefore with anyone born in that zodiac year.
- Marriage-specific rules
- 阴阳不将 days are favoured for weddings specifically; 女命行嫁大利月 keys to the bride's birth branch; the 嫁娶周堂 chart marks positions that make a day unusable.
What can be worked out, and what cannot
A calendar can determine
- The calendar conversion and all four pillars
- Day Officers, the twelve gods, the mansions, clashes and directions
- The fixed blacklists — 三娘煞, 杨公十三忌, 十恶大败日, 四绝, 四离, 四废
Only a 擇日師 — a date-selection master can decide
Everything that depends on the couple's eight characters, which needs birth times and places rather than just dates, and the parents' details too, since some rules concern harm to the in-laws. Above all, the weighing of factors that contradict each other. That is the craft, and it is why masters deliver three to five ranked dates rather than one answer.
A common claim, corrected
An online almanac can tell you your wedding date.
For 1 August 2026 — a day that is simultaneously a 建 day, a black-path 玄武 day and a 未 day — one mainstream automated almanac lists marriage as suitable and another does not. Same date, same tradition, two automated tools, opposite verdicts. There is no algorithm that resolves it; a master resolves it by judgement about which factor dominates for these particular people.
A useful tool here shortlists and explains rather than deciding. In Singapore and Malaysia, date selection is a live paid service at roughly S$150–388, usually arranged by the parents.