What clock your birth time is on

A birth time is a reading from a clock, and what that clock said depends on where it stood and what year it was. Arcus works that out from the place and the date, so you enter the time exactly as your source writes it and nothing needs converting by hand.

This chapter covers where those clocks come from, what happens for births before time zones existed, why another program may disagree, and how to set an offset yourself.