True Solar Time — 真太阳时 zhēn tài yáng shí

True solar time is on by default; you can switch to clock time in Advanced settings.

Open the free BaZi calculator or the related tool to see True Solar Time applied to a real birth chart.

BaZi runs on a solar calendar. The year starts at 立春, months start at the twelve 节 terms and hours follow the sun. This is different from the lunar calendar used for festivals, which is why your BaZi year or month can differ from the lunar date printed on a calendar.

Timing also extends forward: luck pillars change every ten years from a computed starting age, and annual pillars change every 立春. Both are read against the natal chart, so the same year affects different charts differently.

Precision matters near boundaries. A birth a few minutes from a solar term, from 23:00, or from an hour boundary should be checked with true solar time and the exact birthplace; the calculator flags such cases rather than silently choosing one side.

• Using clock time near an hour boundary without checking solar time.
• Rounding the starting age and then comparing exact dates.
• Changing the annual pillar on 1 January.
• Mixing Zi-hour conventions between charts.

Solar terms come from Chinese astronomical calendars; modern calculators use precise ephemerides, so term instants are accurate to the minute. Luck-pillar rules are stated in the same classics as the pillars themselves.

• Hour PillarThe hour pillar covers one of twelve two-hour periods (时辰), starting with 子 at 23:00–01:00.
• Zi Hour (Rat Hour)The 子 hour runs 23:00–01:00.
• Luck PillarsLuck pillars are ten-year pillars that step forward or backward through the sixty cycle from the month pillar.
• Annual PillarThe annual pillar is the stem-branch of a calendar year, changing at 立春.
• Starting AgeThe starting age is when the first luck pillar begins.

The fastest way to understand True Solar Time is to look at real charts rather than memorise rules. Enter a birth date, time and city in the BaZi Calculator, then locate where True Solar Time appears: in a visible stem, hidden inside a branch, in the current luck pillar or in this year's annual pillar. Note the position, because the year pillar is usually read as background and early life, the month pillar as environment and career setting, the day pillar as the self and close partner, and the hour pillar as later life and output.

• Compare two or three charts where True Solar Time is prominent and two where it is absent; write down what differs in the overall balance.
• Check the month branch first: seasonal strength changes how much any factor matters.
• Use the hidden-stems and Ten Gods tables in the calculator output instead of guessing.
• Treat single factors as clues, never as verdicts; classical texts always weigh the whole chart.

Different schools describe True Solar Time with slightly different emphasis. This site follows widely used conventions (solar-term months, true solar time optional, Zi hour setting configurable) and states them openly so you can compare results with a book or another calculator.

True Solar Time is one piece of a larger system. If you are learning BaZi from scratch, the order below builds each idea on the previous one, and every step links to free reference pages on this site.

1. Calculate a chart and confirm the four pillars are correct (checklist).
2. Learn the ten heavenly stems and twelve earthly branches.
3. Find your Day Master and judge its strength with the five elements.
4. Read the Ten Gods in context.
5. Move on to timing with luck and annual pillars.
6. Use the glossary whenever a term is unfamiliar.

BaZi is a traditional cultural system. This page explains how the symbols are defined and read; it does not make scientific claims or predictions about your health, money or relationships.