A mother remembers only that she gave birth near dawn. Was it five o'clock or six? Many people assume that one uncertain hour invalidates the whole chart, but the change has a clear order and a limited scope. Some parts move first, while the parts set by the birth year stay in place.
The Life Palace moves first
The Life Palace is built from both the birth month and the birth hour: count forward from the Yin palace to the month, then count backward from the Zi hour to the birth hour. One hour off can shift the Life Palace by a single palace. That may change the five-element phase and the placement of Zi Wei, so the fourteen major stars settle again along their fixed star chains. The relationships between stars do not break; their positions across the twelve palaces simply move.
Hour-based stars move, year-based stars do not
Several stars are placed directly from the birth hour. Wen Chang counts backward from the Xu palace and Wen Qu forward from the Chen palace, while Di Kong and Di Jie count from the Hai palace. One hour off changes these at once. By contrast, the yearly four transformations, Lu Cun and the Yang/Tuo pair set by the year stem, and Tian Ma set by the year branch, do not move. If a software tool changes those too, the setup or calendar conversion is likely wrong.
Compare the two neighboring hours
Place the two candidate charts side by side. Note whether the Life and Body Palaces shift, then compare the major stars and the Chang, Qu, Kong and Jie placements, and confirm the year-based stars remain identical. If the differences stay within one or two palaces and the person's real history matches one version, there is a basis for choosing. Also rule out software differences: lunar conversion, time zone and the early/late Zi hour rule can all misalign a chart. Fix the year, month and day first, narrow the hour, then confirm with events that have already happened.