Why other apps show a different chart

If your chart doesn't match another app's, it's almost always a convention, not a mistake.

Clock time or Sun time

Many apps use clock time. This app uses your city's true solar time: it corrects for your longitude and the equation of time. In places like Madrid, clocks can run more than two hours ahead of the Sun in summer, and that changes the Hour pillar.

When the day starts

Some schools change the day at midnight; others at 11 pm, when the 子 hour begins. This app uses 11 pm by default.

Historical daylight saving time

Daylight saving rules have changed many times. An app that applies today's rule to a birth decades ago can be off by an hour.

How to compare

In Settings, Calculation conventions changes the convention for every chart. When a chart's hour depends on the convention, that person's page shows a Compare conventions card with the pillars by the sun and by the clock, side by side. From there, "Use clock time for this chart only" switches just that person's chart to clock time. There's also a short comparison at the end of "How we calculated it", on the Chart tab.