Guide
When the Chinese month turns
Why a BaZi month changes at a solar boundary rather than on the first day of the calendar month.
The month follows the Sun
BaZi months begin at sectional solar terms. These are points in the Sun's yearly path, calculated for the relevant year. The turn usually falls several days into the Western calendar month.
A monthly reading therefore changes on the actual boundary. It does not assume that a new influence began at midnight on the first.
The month sits inside larger time
A month is read against the person's birth chart, current ten-year chapter, and current year. The same month can support one chart and press another. Aster starts with the person's actual Day Master rather than a year animal alone.
What the date changes
The turn date tells Aster when to send the monthly letter and when its claims begin. It does not make every day in the month identical. Shorter daily movements can still change which part of the larger pattern is most visible.