Calculators · sun sign
Your true sun sign
Not from a table. This computes where the Sun actually was at the moment you give it, to the minute, and tells you how far into the sign that was.
The offset is the one your birthplace was on that day, including summer time if it was in force. It matters: a few hours is the whole width of a cusp.
How this is computed
A sign is a thirty-degree arc of the ecliptic, and the Sun enters it at a precise instant. That instant is not the same date every year: it moves about six hours annually across the leap-year cycle and drifts across decades, so the March boundary has landed anywhere between the 20th and the 21st over the last century.
Positions come from astronomy-engine (MIT), and are checked against published equinox and solstice tables to within a minute on every build. The zodiac used is tropical — 0° Aries is the March equinox — which is what Western astrology means by a sun sign.
Nothing here is a claim about you. It is a claim about where the Sun was, which is the only part of this subject that can be checked.