The twelve tropical longitude intervals
Each sign owns a half-open interval: its starting longitude is included and the next sign’s start is excluded. Within-sign degree equals the full longitude minus the interval start. The sequence restarts at 0 degrees after Pisces approaches 360 degrees.
| Sign | Full longitude | Within-sign range |
|---|---|---|
| Aries | 0° to <30° | 0°00′ to <30°00′ |
| Taurus | 30° to <60° | 0°00′ to <30°00′ |
| Gemini | 60° to <90° | 0°00′ to <30°00′ |
| Cancer | 90° to <120° | 0°00′ to <30°00′ |
| Leo | 120° to <150° | 0°00′ to <30°00′ |
| Virgo | 150° to <180° | 0°00′ to <30°00′ |
| Libra | 180° to <210° | 0°00′ to <30°00′ |
| Scorpio | 210° to <240° | 0°00′ to <30°00′ |
| Sagittarius | 240° to <270° | 0°00′ to <30°00′ |
| Capricorn | 270° to <300° | 0°00′ to <30°00′ |
| Aquarius | 300° to <330° | 0°00′ to <30°00′ |
| Pisces | 330° to <360° | 0°00′ to <30°00′ |
Boundary examples
29°59′59″ of Aries remains Aries. Exactly 30 degrees full longitude is 0 degrees Taurus. Exactly 0 degrees full longitude is 0 degrees Aries, and 360 degrees is normalized back to 0 degrees before classification. There is no thirteenth interval between adjacent signs and no separate “cusp sign.”
If a time range produces longitudes on both sides of an ingress, the result reports both possible signs. If one exact position lies within 0.10 degrees of either edge, the interface adds a boundary warning so the user can recheck the time and convention.
Degrees, minutes and seconds
One degree contains 60 arcminutes and one arcminute contains 60 arcseconds. The public result normally shows within-sign degrees and minutes because more digits can imply certainty that the birth record does not support. The expanded audit retains an unrounded full longitude for an exact instant.
Notation describes angle, not clock duration: 14°30′ means fourteen and one-half degrees inside the sign. It does not mean fourteen hours and thirty minutes, and it does not identify a house position.
Why the date tables are only approximations
Popular Sun-sign date ranges summarize typical ingress dates, but the exact UTC ingress varies from year to year. A birth near a listed date boundary therefore needs the actual year, local time and historical timezone conversion. The Sun calculator evaluates the longitude instead of assigning a sign from a generic calendar table.
Scope of this reference
This is a coordinate and formatting reference. It does not assign traits to a degree, use decans, degrees of exaltation, Sabian symbols or predictive meanings. Astrology is not scientifically established; interpretations are for entertainment and self-reflection.