How accurate the charts are
Revised . First published .
Planet positions
astronomy-engine gives planet positions to about one arcminute. That's far finer than any sign or house limits. That's roughly one sixtieth of a degree.
Time zone information
Most birth chart errors come from the birth time rather than the planets. Some US cities and states had their own daylight saving rules before 1970. If your result shows an offset that seems wrong for your birth place, compare it with a record from that area.
Limits we know about
Chiron doesn't support dates before 1900 or after 2100. You need an accurate time if the birth happens close to midnight or a sign change of the Moon. Above 66 degrees of latitude, Placidus houses can't be drawn.