What this Sun calculator returns
For an exact recorded time, the result shows the Sun’s tropical sign, degree and minute for the explicitly confirmed UTC instant. The audit includes the unrounded 0–360-degree longitude, coordinate convention, engine version, place, timezone and historical offset.
For an approximate or unknown birth time, the result reports the evaluated interval. A stable outcome gives the sign and degree range observed; an ingress outcome gives every possible sign. Neither path labels the midpoint or a default noon position as exact.
Why zodiac cusp dates vary
The familiar zodiac date ranges are summaries, not fixed astronomical cutoffs. The Sun reaches 0, 30, 60 degrees and the other tropical boundaries at a particular moment. That ingress can occur on a different local date in Dublin, New York or Sydney because each location converts the same UTC event through a different offset.
If a birthday is well away from an ingress, the sign normally stays stable across the day. Near the change, year, time and timezone become part of the answer. The calculator tests those inputs instead of relying on a month-and-day table.
There is no separate cusp sign
In this twelve-sign tropical calculation, every unrounded longitude belongs to exactly one 30-degree sector. A position can be very close to a boundary, but it cannot occupy two Sun signs at one exact instant. “Cusp” is useful here only as a warning that uncertain birth time or timezone may place the evaluated interval on both sides of an ingress.
How the exact Sun longitude is produced
Astronomy Engine calculates a geocentric vector from Earth to the Sun with light-time and aberration handling, then converts it to the true ecliptic and equinox of the requested date. The longitude is classified before any display rounding. This keeps a value such as 29.999 degrees in the correct sign instead of displaying 30.00 degrees under the previous sign.
The selected city does not change the geocentric Sun position itself. It establishes the timezone needed to convert a recorded local birth time into the correct UTC instant.
What happens when birth time is unknown
The calculator evaluates every valid sampled instant from 00:00:00 through 23:59:59 in the confirmed local timezone. Repeated clock labels are evaluated twice because both UTC instants were real. Nonexistent daylight-saving labels are skipped, and a civil date that was entirely skipped returns no result rather than borrowing an instant from another date.
Why Sun-sign results can differ
Check whether both tools use the tropical zodiac, the same city and IANA timezone, the same treatment of daylight-saving history and an apparent true-of-date longitude. A tool that uses only the calendar date may silently choose noon or a fixed date range. This calculator exposes the UTC conversion and boundary warning so the difference can be traced.