Before the world had time zones
Until a country adopted standard time, a town kept its own noon, set by the Sun over that town. A birth from that era belongs on the birthplace meridian, not on a zone that did not yet exist.
Arcus casts those charts on local mean time. A birth in Ulm in 1879 is cast on Ulm's own clock, forty minutes ahead of Greenwich, rather than on Berlin's fifty-three. That is a thirteen minute difference, which is about three degrees of Ascendant.
Some countries put the whole nation on the capital's clock before they took a zone, and Arcus follows that where it happened: France on Paris time until 1911, Ireland on Dublin time until 1916, the Netherlands on Amsterdam's until 1937, Switzerland on Bern's until 1894, and India on Madras time until 1906.
You can see which rule a chart got. The line under the birth data reads Local mean time, with the offset beside it.
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