The degree, and why it is the interesting number
Libra runs from one hundred and eighty degrees of ecliptic longitude to two hundred and ten. Noon on 3 October places the Sun a little over nine degrees into that stretch in some years and a little under eleven in others. The whole spread over more than a century is under a degree and a half, which is small enough that the date is a reliable marker of position and large enough to matter here.
Nothing exotic keeps the figure that steady. The calendar gains a day every fourth year to absorb the quarter day the Earth takes beyond three hundred and sixty five, so the date and the orbit stay roughly aligned instead of drifting apart. Within each four year cycle the position slides forward and then snaps back, tracing the same short arc again and again.
A decan that depends on your year
Each sign is cut into three bands of ten degrees. The first ten degrees of Libra form its opening decan, and the second decan begins exactly at ten. A birthday sitting at nine point three in one year and ten point seven in another lands on both sides of that line, so 3 October is a first decan date in some years and a second decan date in others.
Under the Chaldean order, the opening third of Libra is governed by Venus, which also rules the whole sign, while the middle third answers to Saturn. Tradition treats the first as the most straightforwardly Venusian part of Libra and the middle as the part where the sign's talent for weighing hardens into judgement. Which of those descriptions applies to a given 3 October depends entirely on the year, and the widget above will say which.
What the calendar date does not decide
The Sun is one body. On the same day the Moon moves roughly thirteen degrees, which means it can begin the day in one sign and end it in the next. Two people sharing this birthday can have Moons that do not match, and the Moon is the placement most readings lean on for temperament.
The rising sign is looser still. It changes about every two hours, so all twelve signs come up over a full day, and the one that was on the horizon at your birth depends on the hour and the latitude of the place, not the date. That single placement sets the house framework the rest of the chart is read against. Beside it, a shared sun sign is a thin thing to hold in common.
How the tradition reads the placement
Libra is cardinal air ruled by Venus. Cardinal signs open seasons, and this one opens autumn at the equinox, which is where the association with balance comes from rather than from any quality of the people born under it. Air is read as the mode that works through comparison and exchange, so the sign is described as relational and slow to settle a question before both sides have been stated.
Those are interpretations attached to a position, not consequences of it. The checkable part is the longitude, and everything after that is a reading a tradition has laid over the number. Marked as such, it is still worth knowing which band you sit in, because the decan is what separates one Libra birthday from the next. Venus is also read as the ruler of the whole air triplicity by night in the older scheme, which is one reason the sign carries so much of its ruler in the way it is described. None of that follows from the date, but all of it is what the tradition brings to a position once the position is known.
Questions people ask about this
What sign is 3 October?
Libra, without qualification. The date sits nine or ten degrees inside the sign, well past the equinox boundary and three weeks short of the Scorpio one, so no year in the range checked here puts it anywhere else.
Which decan is a 3 October birthday?
It depends on the year. Noon on this date has fallen either side of the tenth degree since 1930, which is the exact line between the first and second decan of Libra. The widget above resolves it from your birth year and place.
Why does the degree change from year to year at all?
Because the year is not a whole number of days. Each common year the Sun ends up about a quarter of a day further along on the same date, and the leap day pulls it back. The result is a small repeating cycle rather than a drift.
Does the decan change how the sun sign is read?
In traditional practice it adds a second ruler over the top of the first. Venus rules all of Libra, and the middle decan brings Saturn in alongside it. Readings treat that as a shift of emphasis within the sign, not a different sign.
Can two people born on this date have very different charts?
Yes, and usually they do. The Moon can differ by a sign and the rising sign by any of the twelve. Only the Sun and the slower planets are common ground, and those are shared with everyone born the same week.
Is my birth time needed for this date?
Not to establish the sign, which is settled at every hour. It is needed for the rising sign, often for the Moon, and for the exact degree if you want it to a fraction rather than to the nearest whole number.