How close is close
At noon across the years from 1930 to 2035 the Sun on 17 February has been between about twenty seven and three quarters and twenty nine degrees of Aquarius. The remaining distance to the boundary is therefore between one and two degrees, which the Sun covers in one to two days.
Since the year to year variation on a fixed date is only about a degree and a half, and it oscillates rather than drifts, that gap has never closed. Every 17 February in the modern calendar has been an Aquarius birthday at any hour of the day.
The following day is where the question genuinely opens. From 18 February onward the ingress into Pisces starts to fall inside the day itself in some years, which is what makes that date a real boundary case and this one not.
The last degrees of a sign in the tradition
Older writers gave the closing degrees of a sign a name and a character, treating them as the point where the sign's business is being handed over rather than begun. Some medieval material also singles out particular degrees as strong or afflicted, though the lists disagree with one another so completely that they are best read as local convention.
In modern practice the twenty eighth degree of Aquarius is simply a position. It is in the third decan, the band from twenty degrees to thirty that the Chaldean order assigns to the Moon, and it carries whatever that band is read to carry, no more and no less.
Reading a whole personality into a single degree is where most of this material overreaches. The band is a useful way to describe a position more finely than by sign, and it was never meant to carry the weight that modern summaries put on it.
What being near the edge does and does not change
It does not dilute the sign. A Sun at twenty eight degrees of Aquarius is as fully in Aquarius as one at eight, and there is no technique that grades membership by how far along the position sits. The word cusp, when people use it here, describes uncertainty about the facts rather than a blended condition.
What it does change is the aspects. A late degree brings the Sun into contact with planets that an early degree would miss entirely, and it also shifts where in the following sign the solar return will land. Those are real consequences and they all depend on the number rather than the name.
The rest of the chart
The Moon changes sign every two and a half days or so, so on this date it will be in one of two signs depending on the hour. The rising sign turns through all twelve in a day and depends on latitude as well as clock time, which leaves it entirely open until a birthplace is supplied.
The widget above takes your year, time and place, returns the exact solar longitude and reports the distance from your birth to the nearest sign boundary. On this date expect an answer in the region of a day and a half, which is close enough to be interesting and far enough to be certain.
Between them the Moon and the horizon account for most of what separates two charts drawn for the same date, which is why the birth time is asked for so insistently.
Questions people ask about this
Is 17 February Aquarius or Pisces?
Aquarius in every year of the modern calendar. The Sun is around twenty eight degrees into Aquarius and does not reach Pisces for another day or so.
Am I on the Aquarius Pisces cusp?
No. There is no cusp in the technical sense, since the Sun holds one longitude at any instant. On this date that longitude has always been inside Aquarius.
Which date is the real boundary?
Usually 18 or 19 February, where the ingress can fall inside the day itself and the birth hour decides the answer.
Does a late degree mean a weaker sun sign?
No. The degree affects aspects, house placement and the timing of a solar return, not whether the sign applies.
What decan is twenty eight degrees of Aquarius?
The third, running from twenty to thirty degrees, assigned to the Moon under the Chaldean sequence of rulers.
Do I need my birth time?
Not for the sign here, since the margin holds at every hour. You do need it for the Ascendant, the houses and often the Moon.