The day that keeps the two in step
The tropical year, the interval between one March equinox and the next, is about three hundred and sixty five and a quarter days. A calendar of whole days therefore falls behind by roughly six hours a year, and after a century without correction the seasons would have slipped by more than three weeks.
The leap day is the correction. Because it exists, a fixed calendar date returns to nearly the same solar position year after year, which is the reason every page on this site can quote a degree range only a degree and a half wide. The leap day birthday is, in a sense, the mechanism that makes all the others stable.
Where the Sun actually stands
Across the leap years from 1930 to 2035, noon on 29 February has put the Sun between about nine point eight and eleven point two degrees of Pisces. That straddles the ten degree mark, which is the boundary between the first and second decans.
So the sign is settled and the decan is not. Some leap day births fall in the Saturn ruled first band and others in the Jupiter ruled second. Which one applies depends on the year and the hour, and it can only be answered by calculating the position rather than reading it off a table.
In practice that means a leap day birthday needs the calculation more than most. A published date range says Pisces, which is right and unhelpful, while the finer division of the sign genuinely depends on the year.
The two readings on either side of the line
The Chaldean order gives the opening ten degrees of Pisces to Saturn and the following ten to Jupiter. Tradition reads the Saturn band as the disciplined and enduring third of the sign, and the Jupiter band as the open handed one, reinforced by the fact that Jupiter is also the older ruler of Pisces itself.
Those are interpretations attached to a scheme, not conclusions drawn from the position. What the position itself supports is the narrower statement: a leap day Sun is in Pisces, close to the middle of the first half of the sign, and near a divide that most birthday writing never mentions.
The two schemes in circulation also disagree here. The triplicity method assigns this band to a different planet from the Chaldean order, so a decan ruler quoted elsewhere may not match the one given here.
What a leap day does not do to a chart
Nothing about the date affects anything except the Sun. The Moon changes sign every two or three days and can differ between a morning and an evening birth on the same leap day. The Ascendant moves through all twelve signs in twenty four hours, so the rising sign depends on the hour and the latitude alone.
There is also no astrological content in the rarity of the date. A birthday that recurs every fourth year is a fact about the calendar rather than about a chart. The widget above computes the exact degree for your own leap year and birthplace, and reports how far the Sun stood from the nearest sign boundary.
Practically, the solar return falls a little earlier or later than the calendar date in most years, which is the technical answer to the question leap day children are usually asked.
Questions people ask about this
What star sign is 29 February?
Pisces, in every leap year. The Sun entered Pisces around eleven days earlier, so the date is never close to a sign boundary.
What degree of Pisces is a leap day birthday?
Around ten. Noon positions in leap years between 1930 and 2035 range from roughly nine point eight to eleven point two degrees of Pisces.
Which decan does 29 February fall in?
Either, depending on the year and hour. The first and second decans of Pisces divide at ten degrees, and leap day sits right on that division.
Does a leap day birthday mean anything in astrology?
Not in itself. The rarity belongs to the calendar rather than to the sky, and the chart is read exactly as any other chart with a Pisces Sun near ten degrees would be.
Why does the leap day exist at all?
Because the year is close to three hundred and sixty five and a quarter days long. Adding a day nearly every fourth year keeps the calendar aligned with the seasons over long periods.
Is the astrological birthday on 28 February or 1 March in common years?
Neither has any technical standing. The solar return, which is the astrological anniversary, happens when the Sun comes back to its exact birth degree, and that falls at a specific moment regardless of the calendar date.