A boundary that is not a sign boundary
Noon on this date, across 1930 to 2035, has placed the Sun between about eight point eight and ten point one degrees of Pisces. The upper end of that range sits just past the ten degree mark, which is where the first decan ends and the second begins.
So this is one of the rare ordinary dates where something is actually undecided. Not the sign, which is Pisces in every year at every hour, but the ten degree band inside it. Most birthdays sit comfortably inside a decan. This one leans on the line.
It is worth stressing which question is open. Nobody born on this date has any reason to doubt their sun sign. The uncertainty is one layer down, in a division of the sign that most readers have never been told about.
Why it matters which side you fall on
The Chaldean order gives the first decan of Pisces to Saturn and the second to Jupiter, and those are read very differently. The Saturn band is described as the contained and enduring face of the sign, holding its shape under pressure. The Jupiter band is read as the expansive and generous face, and it is also the sign's own traditional ruler, so a placement there gets the same planet twice over.
Whether either description fits a person is interpretation. Which band the Sun occupies is not: it is a number, and it can be checked. Given how many pages skip decans entirely, a reader on this date is unlikely to have been told the question exists.
Why the range is so narrow to begin with
A degree and a half of variation over a century is the product of the leap year rule. Three common years in a row shift the solar position on a fixed date forward, and the leap day pulls it back by close to a full degree, so the value cycles inside a band instead of walking away from it.
It also means the answer depends on where your year sits in that cycle. Years just after a leap day give the lower figures, years just before give the higher ones, which is exactly the pattern that pushes some 28 February births past ten degrees.
Averaged over the cycle the calendar tracks the tropical year to within about half a minute, which is why the Gregorian reform has held since the sixteenth century without further adjustment.
Everything else the date leaves open
The Moon may occupy different signs at different hours of any 28 February, and the rising sign can be any of the twelve, depending on the clock and the latitude of birth. The houses follow from the Ascendant, so the framework of a chart is decided by information the date does not contain.
The widget above takes your year, hour and birthplace and returns the exact solar degree, which on this date is worth having for the decan question alone. It also reports the distance from the nearest sign boundary, which here will be comfortably wide.
The traditional readings attached to either decan are interpretation and are presented here as interpretation. What is not interpretation is the number itself, and on a date this close to a division the number is the only way to answer the question.
Questions people ask about this
Is 28 February Pisces or Aquarius?
Pisces, without exception. The Sun crosses into Pisces around ten days earlier, so no year or time zone places this birthday in Aquarius.
Which decan is 28 February?
Usually the first, occasionally the second. Noon positions across 1930 to 2035 run from about eight point eight to ten point one degrees, and the decan boundary sits at ten.
How do I find out which decan applies to me?
By calculating the actual solar degree for your year, hour and birthplace. The widget above does that, and a result below ten degrees is the Saturn band while anything above is the Jupiter band.
What changes if I am in the second decan?
The Chaldean ruler changes from Saturn to Jupiter, and the traditional reading changes with it, from the contained face of Pisces to the expansive one. The sun sign itself is unaffected.
Why is my degree different from my friend's on the same date?
Because of the birth year and the birth place. The position on a fixed date shifts through the leap year cycle, and local time offsets move it further.
Does 29 February change any of this?
It shifts the following years back down the cycle. A birth on 29 February itself sits a little further along than 28 February in the same year, close to the same decan boundary.