How to use it
- Type your birth date. The result appears as you type.
- If you know your birth time, enter it. Enter your Time zone as hours from UTC as well, for example 3 for Istanbul in summer.
- Read Sun sign, its dates and the traditional meaning. If the result says the Sun changes sign that day, the birth time decides the sign.
- Scroll to the table to see the date each sign started in your birth year.
How the sun sign is found
The sun sign is the tropical zodiac sign in which the Sun appears at the moment of birth. The zodiac is twelve arcs of 30 degrees along the Sun's yearly path, counted from the spring equinox. The calculator takes the Sun's apparent position from astronomy-engine, a published open-source ephemeris library (MIT licence), and finds the day when it crosses each 30-degree boundary.
Because the Earth's orbit is not perfectly regular, the dates of the signs move by a day or so from year to year. That is why the calculator works out the dates for your birth year rather than using fixed calendar dates.
- The Sun enters Aries at the March equinox, Cancer at the June solstice, Libra at the September equinox and Capricorn at the December solstice.
- The dates on the page are the dates of the Sun's entry and the Sun's exit in UTC, not the dates printed in a newspaper column.
Cusp days and the birth time
On a few days each year the Sun changes sign part way through the day. On such a day a birth before the change is in the earlier sign and a birth after it is in the later one. The calculator finds the exact moment of the change and compares it with your birth moment in UTC.
If you do not know the birth time, the page shows both signs and the moment of the change, and the sign is left open. The time zone is needed to turn your local clock time into UTC; without it the page reads your time as UTC and says so.
What the meanings are, and are not
The descriptions of each sign, its element, its modality and its ruling planet come from the astrological tradition of the zodiac. They are descriptions of a traditional character, offered for entertainment and reflection. They are not scientific findings, and they are not a prediction of your life or your health.
Some modern astrologers give Uranus, Neptune and Pluto to Aquarius, Pisces and Scorpio instead of the traditional rulers. The page follows the traditional rulers.
Worked example: 21 May 1990, born at 10:00 UTC
On 21 May 1990 the Sun enters Gemini at 07:37 UTC, so that day is a cusp day: the part of it before 07:37 UTC is Taurus, and the rest is Gemini.
A birth at 10:00 UTC is after that moment, so the sun sign is Gemini, with the element Air, the modality Mutable and the traditional ruler Mercury. The table lists May 21, 1990 at 07:37 UTC as the start of Gemini in that year. Without the birth time, the page shows Taurus or Gemini and leaves the sign open.
For a day in the middle of a sign, such as 15 June 1990, no birth time is needed: the sign is Gemini from May 21, 1990 to June 21, 1990.
Frequently asked questions
Is my sun sign the same as my zodiac sign?
Yes. In everyday use the zodiac sign and the sun sign are the same thing: the sign the Sun was in on the day you were born.
Why do the dates of the signs change from year to year?
The Sun's path is measured against the equinoxes and solstices, and their exact moments shift slightly each year because of the Earth's orbit and the leap-year cycle. The table shows the dates for the year you chose.
What if I was born on the day the sign changes?
Enter your birth time and your time zone. The calculator compares your birth moment with the exact moment of the change. Without a birth time the sign stays open, and both signs are shown.
Does this calculator use the Moon sign or the rising sign?
No. It only finds the sun sign. Your rising sign and Moon sign need your birth time and place and a birth chart calculation, which is a different tool.
Is the time zone field the same as my time zone name?
No. Enter the offset from UTC in hours that applied at your birth, for example 3 or -5, and include summer time if it applied. A place name such as Istanbul is not needed.
Does the calculator send my birth date anywhere?
No. The Sun's position is computed in your browser, and nothing you enter is sent to a server or stored.
Sources
- astronomy-engine, open-source astronomy library used for the Sun's position (MIT licence)
- Wikipedia: Zodiac, the signs and their traditional elements and rulers
Figures and text last checked on Tuesday, November 10, 2026.