Perpetual Calendar QuanBuFang

The exact civil Gregorian time of the 2026 Grain in Ear solar term is June 5, 2026, at 23:48. By ordinary civil calendar dating, it occurs on June 5.

However, our calendar follows a traditional calendrical rule: for both the Gan-Zhi calendar and the lunar calendar, the day changes at Zi hour. In this system, after 23:00, the traditional calendrical day has already moved into the next day. Since the 2026 Grain in Ear solar term occurs at 23:48, it belongs, in our traditional calendrical framework, to the Xin-Hai day, Wu-Zi hour, and the 21st day of the fourth lunar month.

We treat solar terms, the Gan-Zhi calendar, and the lunar calendar as closely connected parts of the traditional Chinese calendrical system. Therefore, in the monthly calendar grid, we place the solar term according to its traditional calendrical position, while still preserving and displaying its exact Gregorian timestamp for verification.

Not necessarily. Many calendars are designed primarily for civil date lookup, so they place a solar term on the Gregorian date on which it occurs. If a solar term occurs at 23:48 on June 5, they show it on June 5.

Our emphasis is different. We focus on the solar term’s placement within the Gan-Zhi and lunar calendrical systems. Under the Zi-hour day-change rule, a solar term occurring after 23:00 belongs to the next traditional calendrical day. The two approaches serve different purposes: one prioritizes civil Gregorian dating, while the other prioritizes internal traditional calendrical logic.

Zi hour runs from 23:00 to 01:00. In many traditional Chinese calendrical and metaphysical systems, a new day does not begin only at the civil midnight of 00:00. Instead, the traditional day begins at Zi hour, starting from 23:00.

For this reason, our algorithm applies the Zi-hour day-change rule to both the Gan-Zhi calendar and the lunar calendar. This affects the day pillar, the lunar date, and the placement of some solar terms within the monthly calendar grid.

Solar terms, the Gan-Zhi calendar, and the lunar calendar all belong to the traditional Chinese calendrical system. Solar terms determine seasonal transitions, Gan-Zhi marks years, months, days, and hours, and the lunar calendar is based on lunar months. They are not isolated labels; together they form a traditional timekeeping structure.

For this reason, we do not treat solar terms merely as notes attached to Gregorian dates. We place them back into their traditional calendrical context. That is why we display the exact Gregorian time, the Gan-Zhi information, and the lunar-calendar placement together.

BaZi charting depends heavily on solar terms and seasonal structure. In the Northern Hemisphere, Li Chun marks the beginning of spring, but the Southern Hemisphere has the opposite seasonal rhythm. A Northern Hemisphere seasonal framework cannot simply be copied over mechanically.

Our Southern Hemisphere charting method handles key elements such as the year pillar and month pillar according to Southern Hemisphere seasonal timing. As far as we are aware, this is a rare Southern Hemisphere BaZi calculation method that is already being used in practice.

Civil time is the clock time defined by time zones. True solar time is closer to the time indicated by the Sun’s actual position at a specific location. Because longitude varies within the same time zone, different places may not share exactly the same solar timing.

BaZi charting is sensitive to two things in particular: the hour of birth and solar-term boundaries. When high-precision charting is required, true solar time helps determine the hour pillar, solar-term transitions, and related traditional calendrical data more accurately. Our BaZi charting algorithm supports true solar time handling to improve calculation rigor.