How the split falls
Eighty nine years of Pisces against seventeen of Aquarius is not an even contest, but it is nowhere near a settled one. The Aquarius years cluster where the drift of the ingress happens to run late, and they are not scattered at random through the century. Two people born on this date twenty years apart can honestly hold different answers, and neither of them has been misinformed.
That drift has a simple cause. A tropical year is about a quarter of a day longer than a calendar year, so the instant the Sun reaches three hundred and thirty degrees of longitude arrives roughly six hours later each year, then snaps back by about eighteen hours when a leap day is inserted. The boundary therefore saws back and forth across a window of about a day and a half. Nineteen February sits near the late edge of that window, which is why the minority answer keeps appearing.
Your clock and your longitude
The ingress into Pisces is one instant for the whole planet. What differs is the local time that instant is given. If it happens at 04:00 UTC on 19 February, then in New York it is still eleven at night on the eighteenth, and a child born there an hour earlier is Aquarius while a child born at the same absolute moment in Berlin is not.
This is the single most frequent source of a wrongly reported sun sign. People take the calendar date on a birth certificate, look it up in a table built for one time zone, and never notice that the table was never about their part of the world. Giving the birthplace along with the date removes the problem entirely.
Nothing sits between the two signs
The Aquarius Pisces cusp is described in a great many places as a temperament, a mixture of the visionary and the dreamy. Astronomically there is nothing there to mix. The Sun has one ecliptic longitude at any given second, and that value is either under three hundred and thirty degrees or over it. A birth ninety minutes before the change is entirely Aquarius; one ninety minutes after it is entirely Pisces.
Treat cusp as a label for a gap in the record. It marks the fact that year, hour or place were never supplied, and it disappears the moment they are. Nothing about a birth close to the change makes the resulting sun sign weaker or less complete than one in the middle of a sign.
Fixed air against mutable water
Aquarius is fixed air, ruled by Saturn in the older scheme and by Uranus in modern practice. Pisces is mutable water, traditionally Jupiter's and now usually assigned to Neptune. They do not share a ruler in either scheme, so the contrast here is sharper than on some boundaries. Fixed air is read as holding a position; mutable water is read as adapting to what is in front of it.
The usual descriptions still overstate the distance. Both signs are read as looking past the immediate and the personal, one through a principle and the other through sympathy, and both are given a reputation for detachment from ordinary ambition. The difference is in method rather than direction.
Whichever way your birth falls, only the Sun is at stake. The Moon, the Ascendant and everything else in the chart are unchanged by which side of the line you were born on. The widget above works it out from your own year, hour and birthplace and tells you how many hours from the boundary you actually were.
Questions people ask about this
Is 19 February Aquarius or Pisces?
Most often Pisces. At noon across the years from 1930 to 2035 it was Pisces in eighty nine years and Aquarius in seventeen. That minority is large enough that you should check rather than assume.
Which years on this date are Aquarius?
They are the years where the ingress ran late, and they follow the four year leap cycle rather than appearing at random. The widget above identifies your own year directly instead of asking you to match a pattern.
Does my birth time change the answer?
It can. In a year where the boundary falls during 19 February itself, a morning birth and an evening birth on the same date give different signs. In the other years the hour makes no difference.
Am I an Aquarius Pisces cusp?
No, because a cusp is not a placement. The Sun holds one longitude at a time and it lies inside one sign. The term describes information you have not been given rather than a blended condition.
Why do calendars print different dates for the start of Pisces?
Because they are rounding a moving boundary to a fixed day, and they choose different roundings. Some also print dates calculated for a time zone that is not yours.
If I turn out to be Aquarius, does the rest of my chart change?
No. Only the Sun's sign is in question here. The Moon, the Ascendant, the planets and the house placements are calculated the same way regardless.