What does it mean to be born on the cusp?
Being born on the cusp means the Sun changed signs on or near your birthday. The change happens at an exact minute, not at midnight, so a date alone can't always settle it. Without a birth time, the machine checks every time zone on Earth for that day, and if the Sun moved, it names both signs.
The Math
Calculated facts only, worked out the same way the machine does it.
- Without a birth time, the machine looks at the whole calendar day in every time zone from UTC−12 to UTC+14. If the Sun crossed into the next sign anywhere in that window, the day is a cusp day and both signs are named.
- With a birth time and a UTC offset, the birth instant is exact, so the cusp resolves to one sign.
- Example from the machine's own tables (1950–2030): Scorpio begins on October 23 or 24, and birthdays from October 22 to 24 have been cusp days in some years.