Two apps may produce different Zi Wei Dou Shu charts for the same birthday. First compare the recorded birth time and location, including time zone and any true-solar-time option. Second check whether the input uses the Gregorian or lunar calendar. Third check how a leap month is handled. Fourth compare the transformation table and whether the display shows natal, decade, or annual transformations.
Near a two-hour birth-time boundary, a small input difference can matter. One app may recognize a leap month automatically while another requires a choice. Save each setting and change one at a time. Only after the calculation rules match should you compare interpretations.