Add the equation of time after longitude
Atlas first forms local mean solar time from UT1 plus the longitude correction. It then forms local apparent solar time by adding the engine’s equation of time. The saved receipt labels this quantity “apparent minus mean” in seconds: a positive value moves the apparent clock later than the mean clock, and a negative value moves it earlier.
The equation of time is not a timezone adjustment and it is not a fixed yearly constant. It represents the varying difference between apparent and mean solar time. Atlas records the value returned for the calculated instant rather than presenting a current value as if it applied to every birth date.
Why a small correction can matter
The apparent correction can leave all four pillars unchanged, or it can move a displayed time across an hour-branch or day-boundary edge. Atlas recalculates both 00:00 and 23:00 variants after the apparent clock is formed. At 23:00, its implemented rule advances the displayed cycle date; the hour stem follows that displayed cycle day.
Some schools handle late Zi differently, including approaches that retain one day pillar while using the following day’s stem for the hour. That third arrangement is not one of the Atlas rows. A changed apparent-solar result identifies the effect of this named implementation, not a universal rule for every BaZi lineage.
Compare records without flattening the clocks
For a useful comparison, hold the birth instant and coordinates fixed, then read the civil, local-mean and local-apparent rows with the same day boundary. Record which pillar cells and cycle dates change. If the input time is rounded, estimated, or unknown, preserve that uncertainty; a solar-clock conversion cannot recover a missing instant.
Local apparent solar time is offered because some sources request an apparent-solar convention. It is not a general claim that a sundial-like clock is better than civil or mean solar time. The visible result remains a limited Four Pillars calculation with separately sourced interpretive material.
Word origin · etymology
Descriptive astronomical phrase.
Local specifies the place and apparent refers to the observed-looking Sun. The wording distinguishes sundial-like time from a mean-Sun clock.
How we know · epistemology
Apparent solar clock
The Sun's actual apparent position determines this time scale. It differs seasonally from a uniform clock, so a conversion needs the equation of time as well as longitude rather than only a timezone offset.
Explore it in your atlas
Connected concepts
Read alongside this entry
Terms used in this explanation
Mentioned in 2 other entries
These links connect subjects and terminology. They do not establish a shared historical origin.
Sources & provenance
Use the citations beside each section to distinguish a calculation convention, a historical teaching and an editorial example.