Aquarius dates20 January to 18 February, give or take a day

The usual answer, 20 January to 18 February, is a rounding of a moving target. The Sun enters Aquarius when its apparent longitude reaches 300°, and that instant lands about six hours later each year, then jumps back a day in every leap year. Where you were born then decides which calendar date that instant falls on.

For a birth in the eastern United States, the Sun entered Aquarius on 20 January in 59 of the 80 years from 1951 to 2030 and on 19 January in the other 21. It never once began on 21 January in US Eastern time, though some popular tables still print that date. In the UK the split was 69 years on 20 January, 7 on the 19th and 4 on the 21st, and those four were the leap years 1952, 1956, 1960 and 1964. Sydney sits eleven hours ahead of London in January, so there Aquarius begins on 20 January (47 years) or 21 January (33 years) and never on the 19th.

The other end behaves the same way. The Sun leaves Aquarius, and Pisces begins, on 18 February in 54 of the 80 years in US Eastern time and on 19 February in 26. So "Aquarius ends on 18 February" is true in the sense that the last full day of Aquarius is usually the 17th, and the 18th is the handover day.

The drift: why the dates your parents learned are a day late

The calendar is not quite in step with the Sun. Between century corrections it runs on a plain four-year leap cycle, which averages 365.25 days, about 11 minutes longer than the tropical year from equinox to equinox. So within a century every ingress creeps earlier, by roughly three-quarters of a day per hundred years. The Gregorian calendar resets this by skipping the leap day in 1700, 1800 and 1900. It did not skip 2000, so the creep has run on since 1900 and will not be reset until 2100.

You can see it in the January cusp. In US Eastern time:

The February end has moved further. Pisces began on 18 February (US Eastern) in 4 of the 10 years of the 1950s and in 10 of the 10 years from 2021 to 2030. A table written in 1960 that said "Aquarius, 20 January to 19 February" was a fair summary then. For a US birth now it is a day out at the end.

Find your birth year, then compare your birth time with the time in your zone. Born after the Aquarius time and before the Pisces time, you are an Aquarius. The four-year rhythm is easy to spot: the latest starts fall in leap years (2000, 2004, 2008) and the earliest in the year after one (2001, 2005, 2009), because a January ingress comes before that year's 29 February.

Every date from 21 January to 17 February is Aquarius in every year from 1951 to 2030 in all four US time zones. Outside that window it depends on the year. This table counts the 80 years 1951 to 2030 and says what each cusp day was:

Read the row for your birthday and you'll see why "cusp" is a poor word for it. A person born on 20 January in New York in a year when the Sun moved at 3:30 am is an Aquarius if born at breakfast time and a Capricorn if born at 2 am. There is no blended sign, and the tradition never had one. What does exist is a Sun in the first degree of Aquarius, which is an Aquarian Sun that has only just changed sign, and a Sun at 29° Capricorn, which has not. If you don't know your birth time, a Sun within a few hours of the change is honestly undecided. The zodiac sign calculator settles it from your date, time and birthplace, and the January zodiac signs and February zodiac signs pages go through every day of both months.

Aquarius covers two months: the last twelve days of January and most of February, roughly 20 January to 18 February. About 39% of the Sun's time in Aquarius falls in January and 61% in February. If you are asked for "the Aquarius month", February is the better answer.

The Sun spends 29.58 to 29.60 days in Aquarius, 29.59 on average over 1951 to 2030. Only Capricorn (29.44) and Sagittarius (29.55) are shorter. The reason is orbital: Earth passes perihelion, its closest point to the Sun, in early January, and moves fastest then, so the Sun appears to cross the winter signs more quickly than the summer ones. Cancer, crossed near aphelion in July, takes 31.45 days.

Each sign splits into three 10° decans. The dates below are the usual ones in UTC; they slide by a day like the sign itself.

Two systems are in use and they disagree. The older one assigns each decan a planetary "face" in Chaldean order, running from Mars at 0° Aries, which gives Aquarius Venus, Mercury and the Moon. The modern scheme assigns each decan to a sign of the same element, which gives Aquarius, Gemini and Libra, and through them Uranus or Saturn, Mercury and Venus. Pages that give the Aquarius decans as Uranus, Mercury and Venus are using the modern scheme, usually without saying so, and pages that give Venus, Mercury and the Moon are using the faces. Neither changes the sign; the decan is a refinement within it.

The Sun returns to Aquarius every year, but the slow planets do not. Some Aquarians were born with an outer planet in their own sign, and the years are exact. All dates below are DE442 ingresses, UTC.

Two runs stand out. An Aquarius born between 29 January 1998 and February 2003 has the Sun, Uranus and Neptune in Aquarius together, three planets in one sign for everyone born in those weeks; the stellium guide explains how to read a cluster like that by house. And the Jupiter-Saturn conjunction that opened the current twenty-year cycle was exact on 21 December 2020 at 18:21 UTC at 0°29′ Aquarius, so 2021 Aquarians were born a month after it with both planets still in their sign.

Not very, but less common than average. In the Shymea rarity study, which assigns 62,187,026 registered US births from 2000 to 2014 to the exact ingress instants, 4,932,117 were Aquarians: 7.93%, eleventh of the twelve signs. Only Capricorn (7.63%) was rarer. A perfectly even spread would give each sign 8.33%.

Two things push Aquarius down. The Sun spends only 29.59 days there, so on astronomy alone Aquarius would hold 8.10% of births (the 2014 figure in the study). Births are also slightly scarcer than average in late January and early February, so the real share in 2014 was 7.93%, a ratio of 0.979. Other registries agree: Aquarius was 8.08% of births in England and Wales in 2025 (tenth), 7.92% in Canada in 2024 (ninth), 8.07% in Australia in 2023 (tenth) and 8.00% in New York City in 2024 (eleventh).

For the next few years the story for Aquarius Suns is Pluto. Pluto settled in Aquarius on 19 November 2024 and crosses about 5° of the sign every three years, and its retrograde loops take it over most degrees three times or more. Roughly, by birthday (the date of each degree moves by a day with the year):

In 2027 Pluto turns retrograde on 8 May at 7°11′ Aquarius and direct on 18 October (UTC) at 4°45′, so birthdays from about 24 to 27 January get the contact this year.

The Sun enters Aquarius on 20 January 2027 at 07:30 UTC (2:30 am Eastern) and leaves on 18 February at 21:33 UTC (4:33 pm Eastern). An annular solar eclipse falls on 6 February 2027 at 15:56 UTC at 17°38′ Aquarius, on the Sun degree of people born around 6 February, and a penumbral lunar eclipse on 17 August at 24°12′ Aquarius. Jupiter spends the first seven months in Leo, the sign opposite, until 26 July 2027. The Aquarius 2027 horoscope has the full year in dates, and the Aquarius horoscope the current week.

Compatibility by Sun sign is a weak signal, and the classical reasons are more interesting than the usual tables. Leo is the opposite sign: the Sun's own house facing the Sun's detriment, so Leo and Aquarius is a pairing of one person who wants the stage and one who would rather run the lighting desk. Gemini and Libra share Aquarius's triangle under Saturn and Mercury and sit a trine away, the easiest aspect. Capricorn shares Saturn as ruler, and Pisces is the next sign along, but both are neighbours, and in the tradition adjacent signs are in aversion: 30° apart, they make no aspect and do not "see" each other. Neighbours can get on perfectly well. They just have less in common than the shared ruler suggests. A real comparison needs two whole charts, which is what synastry does.

The neighbouring signs have their own pages: Capricorn and the 19 January cusp and Pisces from 18 February. All twelve signs, with the same year-by-year data, are on the zodiac signs by date page.