The settled part
At noon in each year from 1930 to 2035, the Sun on this date stood between roughly twenty three and twenty four and a half degrees of Libra. The sign is not in question in any of those years and the degree moves very little, so both facts can be stated without hedging.
The reason the degree holds still is mechanical. A common year is about a quarter of a day shorter than the orbit, which pushes the Sun's arrival later by around six hours annually, and the leap day pulls it back by close to a full day every fourth February. The two corrections nearly cancel, leaving a swing of a little over a degree and no long term drift.
The face inside the sign
Within the settled part there is one more layer worth naming. Each sign splits into three faces of ten degrees, and a position past twenty degrees falls in the last of them. The Chaldean order gives that band of Libra to Jupiter; the triplicity scheme reaches Mercury instead, by way of Gemini. Both attributions are traditional and they do not agree, which is worth knowing before trusting a single quoted ruler.
This is also the only layer that distinguishes one Libra birthday from another without leaving the sun sign behind. Two Libra birthdays a fortnight apart sit in different faces and pick up different attributions in the older sources, even though every popular description of them is identical.
What the tradition reads into the band is interpretation and belongs in a different category from the position. The reading can be repeated, compared against other sources and argued about; the longitude can be calculated and checked. Keeping the two apart is most of what separates a useful page on a birthday from a decorative one.
The Moon is wide open
The Moon crosses the zodiac in a little under a month, which means it returns to no fixed place on a calendar date. On this date across different years it can be found in any of the twelve signs with no pattern a birthday can capture. Within a single 17 October it moves roughly twelve to fifteen degrees, so a birth at breakfast and a birth at midnight can land in neighbouring signs.
Nothing about the date narrows this down. It takes the year and the hour, and where the Moon is close to changing sign it takes the birthplace too, since the local clock decides which side of the change a given moment fell on.
This is the placement most often reported wrongly when only a date is available, and it is the one traditional practice weighs most heavily after the Sun and the ascendant. A stated Moon sign that came from a date alone should be treated as a guess until the hour is supplied, particularly for anyone born within a few hours of a sign change.
The rising sign and the houses
The ascendant is the degree of the zodiac coming over the eastern horizon at the moment of birth, and the earth's rotation carries it through all twelve signs in a day. Two people born on this date four hours apart have different rising signs and a completely different arrangement of houses, which relocates every planet in the chart into different areas of life.
So the sun sign turns out to be the least personal component rather than the most, because it is shared with everyone born in the same stretch of the year across all of history. The widget above computes the exact solar degree from your own year, hour and birthplace, and reports the distance from that position to the nearest sign boundary.
Questions people ask about this
What sign is 17 October?
Libra. In every year sampled at noon from 1930 to 2035 the Sun was well inside the sign, with the change into Scorpio still several days ahead.
How precise is the degree for this date?
The noon figure stays between about twenty three and twenty four and a half degrees of Libra across that century. Your personal value falls inside that band and depends on the year, hour and place of birth.
Can the Moon be worked out from the date alone?
No. The Moon changes sign every couple of days and covers the whole zodiac in under a month, so the same calendar date gives a different position in every year.
Which decan of Libra is this?
The third, from twenty to thirty degrees. It is given to Jupiter in the Chaldean order and to Mercury through the Gemini association in the triplicity scheme.
Why is the rising sign not fixed by the date?
Because it depends on the rotation of the earth rather than its orbit. All twelve signs rise over the course of a day, so the hour and the latitude of birth decide it.
Is a Libra sun the most important part of my chart?
It is the part 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.