The one thing the date fixes
At noon in each year from 1930 to 2035, the Sun on this date stood between roughly four and five and a half degrees of Scorpio. The sign is not in question in any of those years, since the ingress falls around 23 October and never comes near enough to this date to matter.
The degree holds still because the calendar and the orbit stay in step. A common year is about a quarter of a day short, so the Sun arrives at a given longitude some six hours later each time, and the leap day every fourth February pulls the whole count back by nearly a day. Over the cycle the two effects come close to cancelling and the residual is a swing of a little over a degree.
Even that figure is not quite final for an individual, because the Sun advances close to a degree between one midnight and the next. A birth before dawn and a birth late in the evening on the same 28 October differ slightly, which is small against the width of a sign and large enough to matter for aspects.
The Moon is not fixed
The Moon crosses the zodiac in a little under a month, which means a calendar date has no purchase on it. On this date in different years it has been in every sign of the zodiac with no pattern that a birthday can capture. Within a single 28 October it covers twelve to fifteen degrees, so a birth in the morning and one late at night can fall in adjoining signs.
Pinning it down takes the year and the hour, and near a sign change it takes the birthplace as well, because the local clock decides which side of the change a given instant fell on. This is the placement most often reported wrongly when only a date is available.
The ascendant and the houses are not fixed
The ascendant is the degree rising over the eastern horizon at the moment of birth, and the earth's rotation carries it through all twelve signs in twenty four hours. Two births on this date four hours apart have different rising signs, and the rate at which signs rise also depends on latitude, so the birthplace changes the answer as much as the clock does.
Because the houses are built outward from the ascendant, changing it rearranges the whole chart. The same planets end up in entirely different sectors, which in traditional practice is at least as consequential as which sign they sit in. None of this can be recovered from a date.
Nor is the aspect pattern fixed. The angles between the planets depend on where each of them stood at the moment of birth, and the faster bodies move enough within a single day to form and break relationships between morning and night. A date gives you the slow half of that picture and none of the quick half.
What is left of the fixed part
Within the settled placement there is one further layer. Below ten degrees the Sun sits in the opening face of Scorpio, given to Mars in the Chaldean order and to Scorpio itself in the triplicity scheme, which sends it to Mars traditionally or Pluto in modern usage. That face is the finest distinction a birthday alone can support.
Everything past it needs the hour and the place. The widget above takes those, returns your exact solar degree rather than a range, and reports how far that position stood from the nearest sign boundary, which is the figure that tells you whether the answer is comfortable or close.
Questions people ask about this
What sign is 28 October?
Scorpio, in every year sampled at noon from 1930 to 2035. The Sun entered the sign around 23 October in all of them, so the date sits several days inside it.
What does a birthday actually determine?
The Sun's position, and very little else. The Moon, the ascendant, the houses and the aspect pattern all depend on the hour and the place of birth as well as the date.
What degree of Scorpio is 28 October?
Between about four and five and a half degrees at noon over that century. Your own figure sits inside that band and depends on your year, hour and birthplace.
Can I find my rising sign without a birth time?
Only approximately. Since all twelve signs rise in a day, the hour is what decides it, though a known place and a narrowed window can sometimes rule several out.
Which decan is this date in?
The first decan of Scorpio, zero to ten degrees. The Chaldean count gives it to Mars and the triplicity scheme gives it to Scorpio itself.
Is the sun sign the most important placement?
It is the most widely shared, which makes it the least distinguishing. Traditional practice weighs the ascendant and the condition of the chart ruler at least as heavily.