What a cusp date changes

A cusp date is the calendar day when the Sun crosses from one sign into the next. The crossing happens at a clock time, and that time shifts from year to year. The same date, such as December 22, can be Sagittarius in one year and Capricorn in another.

The printed range on a sign page is the usual span for people born away from the edge. It does not settle a birthday that falls on the first or last day. Saying someone is "on the cusp" as a mixed personality is a later habit. The astronomical fact is simpler: one clock time, two possible slices.

How the date pages treat it

Each birthday page lists noon UTC from 1992 to 2032. On a cusp it also lists the changeover time in UTC for each year that has one. Noon is a snapshot, not a birth time. If you know the hour you were born, put that hour into the calculator instead of reading noon as the final word.

December 22, November 22, January 19, and October 23 are the well known edges. Other months have them too. The kicker on the date page names the two signs in the order the Sun actually travels, from the sign it leaves to the sign it enters.

Where to check it

Open the birthday page, or use the zodiac sign calculator with the year and the birth time. The Aries and Taurus guides show the two sides of one of those edges.