What is my sun sign?

Your Sun sign is the 30° tropical slice that contained the Sun at your birth. People ask “what is my sun sign?” because it is the one astrological fact that newspapers, apps and casual conversation all share. You find it from the birth date. The Sun moves about one degree per day and changes sign around the same calendar dates each year, with a little drift near the cusps.

SideraChart measures the Sun in the tropical zodiac, from the March equinox, using astronomy-engine (VSOP87). That is Western practice. A sidereal (Vedic) Sun sign can differ by about one sign today because the star-based zero point has precessed. If a friend in a sidereal app reports a different Sun, you are not looking at the same coordinate system.

The calculator converts your civil birth date and time to Universal Time, then reads the Sun’s apparent ecliptic longitude. The sign is longitude divided into twelve 30° blocks starting at 0° Aries (the equinox). On a cusp day — when the Sun changes sign — the clock time and timezone decide which side you are on. Those are the only days when “I am a cusp” is a calculation question rather than a vibe.

Place barely matters for the Sun’s sign. Time matters on the cusp and for the Sun’s degree and house. If you only want the sign and you were not born on a sign-change date, the birthday is enough. If you were born on the changeover, enter the real time or mark it unknown and treat the result as unresolved until you have a clock.

The Sun is one body. A natal chart also has the Moon, Mercury, Venus, Mars and the outer planets, plus the Ascendant if you have a birth time. Two Leos can share a solar month and still not share a Moon, a rising sign, or a house pattern. Sun-sign descriptions survive because they are easy to index, not because they exhaust the sky.

Read the Sun as the daylight plot: what you are doing when you are most obviously yourself in public time. Then read the rest. A chart that only lists the Sun is a headline. The tables under SideraChart’s wheel are the article.

The Moon changes sign every two and a half days, so many people born in the same solar month do not share a Moon. The rising sign changes about every two hours and needs the birth time and place. Together these three are the Big Three. If you only know the Sun, you know the slowest of the three.

You do not need a birth time for a typical Sun sign. You often do not need one for the Moon unless it changed sign that day. You always need one for the rising sign. SideraChart’s dedicated Sun, Moon and rising tools are filters on the same engine as the full natal chart. Use the full chart when you want houses and aspects as well.

There is no extra thirteenth sign in tropical practice, and there is no official dual citizenship on the boundary. The Sun is in one sign or the other at the minute of birth. If you lack a time on a cusp date, say so. Do not average two signs into a custom identity and then treat it as a calculated fact.

Timezone history matters more than people expect. A birth recorded as 23:40 in a city that was still on daylight-saving can be a different Universal Time than the same clock reading in winter. SideraChart uses IANA rules for that date. If an old paper used a different offset, the Sun’s degree can shift; on a cusp, the sign can too.

Enter birth date, and add time and place if you have them. The Sun row in the table is the sign and degree. The wheel places the solar glyph on that longitude. Aspects to the Sun use the same orbs as the rest of the chart: 8° conjunction and opposition, 6° square and trine, 4° sextile.

Save the natal chart if you want the written report and the daily cabinet. Transits to your natal Sun are later weather, stored at noon in the natal timezone. They do not change the natal Sun sign. The Sun sign is a birth fact. Everything else is reading.