Why printed and online almanacs disagree
Two almanacs can agree on a lunar date and disagree about marriage, a direction or a favourable hour. They may be using different kinds of data, different boundary conventions or different editorial rules. A useful comparison starts with the field that differs, rather than treating the whole calendar as one result.
Different kinds of data
A date conversion asks which lunar year, month and day correspond to a civil date. A solar-term calculation asks when the Sun reaches a specified longitude. Yi and Ji add a different layer: a traditional classification of suitable activities and activities to avoid. Agreement on the astronomical calculation does not require agreement on the activity rules.
The Atlas looks up daily activities in its calendar library’s almanac tables. This lookup is separate from the calculations that locate new moons and solar terms. Another almanac may use a different activity table or give different weight to the traditional conditions associated with a day.
Even similar-looking labels can answer different questions. A day officer belongs to the sequence beginning Jian, Establish, and Chu, Remove. A presiding deity belongs to another twelve-part sequence. Yellow path and Black path classify the latter. “Balance” and “Director of Destiny” can therefore appear together without conflicting.
| Field that differs | Possible reason | What to compare |
|---|---|---|
| Lunar day or month | A different civil date, reference time or leap-month designation | The full date and calendar convention |
| Year Ganzhi | A boundary at Chinese New Year or Beginning of Spring | The rule used to begin the stem-and-branch year |
| Month Ganzhi | A lunar-month convention or a solar-term boundary | The kind of month and whether the boundary uses a date or an instant |
| Day Ganzhi near 23:00 | A midnight boundary or a late-Rat boundary | The clock time and the day-pillar convention |
| Yi or Ji | Different activity tables, terminology or month inputs | The exact activity and daily or hourly scope |
| Deity direction | A different named deity, time interval or traditional variant | The deity’s name and the direction scheme |
| Overall favourable grade | An edition’s method of combining classifications | The explanation of that grade in the edition |
Boundary conventions
A solar-term boundary: September 7, 2026
White Dew occurs on September 7, 2026 at 22:41, UTC+8, rounded to the minute. It marks the beginning of the You seasonal month. September 7 is still in lunar month 7, whose successor begins on September 11.
At noon on September 7, the term has not yet occurred, but its civil date has begun. A calculation that changes the month at the start of the term’s date has already moved forward. One that waits for the term’s precise instant has not.
| Item at September 7, 2026, 12:00, UTC+8 | Result |
|---|---|
| Gregorian date | September 7, 2026 |
| Lunar date | Month 7, day 26 |
| Ganzhi month using the beginning of the jie date | Ding-You 丁酉 |
| Ganzhi month using the precise jie instant | Bing-Shen 丙申 |
The two month inputs can produce different almanac classifications while leaving the lunar date unchanged. A daily page using the date-based convention can also keep one month label throughout a day when a time-specific calculation changes labels partway through it.
Only the twelve jie terms begin these seasonal months. They alternate with the twelve principal terms. Autumn Equinox, for example, is a principal term and does not begin another Ganzhi month between White Dew and Cold Dew.
Civil dates and late Rat time
Rat time spans 23:00–01:00. Its first hour falls before midnight and its second after it. Some day-pillar calculations advance the stem-and-branch day at 23:00, while others retain the current civil day until midnight.
The Atlas’s engine provides both treatments. Its ordinary daily Ganzhi remains tied to the civil date. The advancing convention is used in the calculation of the hour’s stem and branch and in several hourly classifications. A late-night difference therefore depends on which field is being compared. It need not mean that the lunar date has changed.
Reference time and historical dates
An instant has different clock readings in different time zones. A date label, by itself, is not an instant. Comparing a date in one zone with a timestamp converted into another can select different civil days before any almanac rule is applied. Events close to midnight are particularly important because the reference date containing a new moon becomes lunar day 1.
Early dates introduce a further distinction. The Atlas’s engine uses Julian civil dates through October 4, 1582, followed by Gregorian October 15, 1582. A proleptic Gregorian converter extends Gregorian rules backwards instead, so an identical early date label can identify a different day. This software convention does not establish which calendar was used in a historical Chinese record.
Printed editions and editorial choices
A printed almanac combines a compiler’s calendar material with a publisher’s choice of layout, supplementary sections and explanations. Two books may share calendar material while presenting different sets of activities. One may offer a general grade where another prints several separate classifications.
A missing activity can also have different meanings. A compiler may omit less commonly consulted activities to save space, or explain a general rule for matters not listed. An online table’s “None listed” field does not automatically inherit that printed edition’s rule. The explanation attached to the edition determines how its omissions should be read.
Translation can create an apparent conflict. Nacai, formal proposal gifts, and jiaqu, marriage, may both be shortened to “wedding.” A translation that merges them makes two distinct entries look like competing judgements about one activity. Keeping the original label visible resolves that kind of mismatch.
A comparison is most informative when it records the full date, the field, the original activity or classification, and the edition or software convention. Once those match, a remaining difference belongs to the rules or data being used. Counting unrelated favourable labels elsewhere on the page cannot resolve it.