Why the question exists
Zi Wei Dou Shu was designed in a China that ran on one time. Today a birth certificate in Toronto records Toronto time — but the calendar engine behind the chart speaks Beijing time. Somewhere between the certificate and the engine, a conversion has to happen, and schools disagree on how.
Three conventions exist: use Beijing time as-is (convert the clock reading), use local mean time (the chart follows the location), or use true solar time (correct for longitude and the equation of time — the classical astronomical answer).
What difference it makes
The birth hour determines the Ming Palace — the anchor of the whole chart. A timezone or solar-time correction that crosses a two-hour boundary changes the Ming Palace, and with it every palace assignment and every reading. For births near an hour boundary, this is not a nuance; it is a different chart.
Our answer
FateZiwei lets you set the birth timezone, converts to Beijing time for the calendar engine, and optionally applies true-solar-time correction by birth city. The chart page always shows which convention was applied — so two practitioners can argue about method while looking at the same honest arithmetic.