Usually Gemini, but not always. In US Eastern time the Sun was in Gemini all day on 21 May in 39 of the 80 years from 1951 to 2030, and changed from Taurus during the day in the other 41. In the UK the change fell during 21 May in 58 of those years, so a British 21 May birthday often needs the birth time.

Astrologically, no one is two signs: the Sun is in one sign or the next at any given minute. You were born on a cusp day if the Sun changed sign on your birth date in your birthplace's time zone. The calculator says so when it happens and gives the minute, and it flags births within 36 hours of a change, where a wrong birth time could flip the sign.

What is my zodiac sign if I don't know my birth time?

On most dates the time does not matter and the calculator gives one sign. If the Sun changed sign during your birth date, it gives both signs and the time of the change in your zone. If you were born near one end of that day, a relative's memory of morning or evening is often enough to settle it.

Why does another website give me a different star sign?

Usually because it uses a fixed date table rather than the year's actual ingress, or a different time zone. A table that says Gemini starts on 21 May was close to right in the 1950s; in US Eastern time Gemini began on 20 May in 8 of the 10 years from 2021 to 2030. Sites using sidereal astrology give a different sign altogether, because they measure from the stars; this calculator is tropical, like all Western astrology.

Does the place of birth change my sun sign?

Only on a cusp day. The Sun changes sign at one instant for the whole planet, but that instant is a different clock time and sometimes a different date in each zone. In 2026 the Sun entered Gemini at 8:37 pm on 20 May in New York and at 1:37 am on 21 May in London, so two babies born at the same moment got different birthdays, and the same sign.

Urania's Mirror, London 1824 · Library of Congress

Free tool · Sun sign

Zodiac Sign Calculator: your star sign, to the minute.

Enter a birth date to get the Sun sign. Add the time and birthplace if you were born near the 19th to 24th of a month, when the Sun changes sign and the clock decides.

Most sign tables print one fixed range per sign, such as Gemini from 21 May to 20 June. The Sun does not keep to that. It enters each sign at a particular minute that moves by up to a day from year to year, and the calendar date of that minute depends on where you were born. This calculator uses the computed minute for every sign change from 1950 to 2030 and converts it into the birthplace's own clock, daylight saving included.

On about 28 days of each month the answer is the same for everyone, whatever the year or the hour. On the two or three days around a change it is not. Leave the time blank on one of those days and the result shows both signs and the exact cutover in your zone, so you can compare it with the time on a birth certificate.

How the sign is worked out

Every Sun ingress from 1950 to 2030 was computed from NASA JPL's DE442 ephemeris as the instant the Sun's apparent position reached 0° of a tropical sign, then rounded to the nearest minute. The same file gives the 10° marks used for the decan. Published USNO equinox and solstice times for 2000 and 2024 to 2026 match to the minute.

Your local birth time is converted to Universal Time with the IANA time-zone rules your browser already holds, so a 1974 British birth or a US birth in a year with unusual daylight saving dates is handled correctly. The degree shown is interpolated between 10° marks and is good to about a minute of arc. The calculation runs on this page; the only thing sent anywhere is the text of a place search.

Common questions

What sign is 21 May?: Usually Gemini, but not always. In US Eastern time the Sun was in Gemini all day on 21 May in 39 of the 80 years from 1951 to 2030, and changed from Taurus during the day in the other 41. In the UK the change fell during 21 May in 58 of those years, so a British 21 May birthday often needs the birth time.
Am I a cusp sign?: Astrologically, no one is two signs: the Sun is in one sign or the next at any given minute. You were born on a cusp day if the Sun changed sign on your birth date in your birthplace's time zone. The calculator says so when it happens and gives the minute, and it flags births within 36 hours of a change, where a wrong birth time could flip the sign.
What is my zodiac sign if I don't know my birth time?: On most dates the time does not matter and the calculator gives one sign. If the Sun changed sign during your birth date, it gives both signs and the time of the change in your zone. If you were born near one end of that day, a relative's memory of morning or evening is often enough to settle it.
Why does another website give me a different star sign?: Usually because it uses a fixed date table rather than the year's actual ingress, or a different time zone. A table that says Gemini starts on 21 May was close to right in the 1950s; in US Eastern time Gemini began on 20 May in 8 of the 10 years from 2021 to 2030. Sites using sidereal astrology give a different sign altogether, because they measure from the stars; this calculator is tropical, like all Western astrology.
Does the place of birth change my sun sign?: Only on a cusp day. The Sun changes sign at one instant for the whole planet, but that instant is a different clock time and sometimes a different date in each zone. In 2026 the Sun entered Gemini at 8:37 pm on 20 May in New York and at 1:37 am on 21 May in London, so two babies born at the same moment got different birthdays, and the same sign.

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Sun ingresses are computed from the JPL DE442 ephemeris in the tropical zodiac, 1950 to 2030, to the nearest minute. Readings are educational, drafted from the computed factors and edited by the Shymea team; they are not the work of a named practising astrologer and are not medical, legal or financial advice. See the editorial policy.