Two rulers over the same position
Rulership in traditional practice works in layers. The sign takes the outer layer, so anything between one hundred and eighty and two hundred and ten degrees of longitude is Venusian. The decan takes the inner one, and the ten to twenty degree stretch of Libra is Saturn's under the Chaldean order that runs the planets from slowest to fastest through the whole zodiac.
Neither cancels the other. A reading takes the sign as the setting and the decan as the accent within it, which is why a birthday in the second decan is described differently from one in the first even though both are simply Libra on a chart summary.
What the tradition says about this band
Venus is read as the principle of relation, proportion and preference. Saturn is read as the principle of limit, duration and standard. Put together over the middle of Libra, tradition describes a stretch where the sign's habit of weighing becomes something closer to holding a line: fairness with a threshold in it rather than agreement for its own sake.
That is an interpretation and should be held as one. The measurable claim is only that the Sun stood at a particular longitude, and the Saturn attribution comes from a scheme worked out long before anyone could check it against anything. It is worth knowing because it is the layer of the tradition that actually distinguishes one date from another, not because the attribution has been demonstrated.
How stable the position is
Across the years from 1930 to 2035 the noon degree on this date varies by about one and a third. The leap year cycle is the reason. Each common year the Sun reaches a given calendar date about a quarter of a day further behind, and February's extra day gives that back, so the position circles a short arc instead of drifting.
Because the whole variation is well inside the second decan, this birthday keeps the same decan in every year of the range. That is not true of every date. Around the tenth and twentieth degrees of a sign the noon figure straddles a division and the band genuinely depends on the year, but a birthday near fourteen degrees is not one of those.
The parts the date leaves untouched
The Moon covers roughly thirteen degrees in a day and changes sign every couple of days, so this date does not pin it down. The rising sign is not narrowed at all: the whole zodiac crosses the eastern horizon in a rotation, and only the hour and the latitude of the birthplace select one. Both of those change a reading more than the sun sign does.
What the date does deliver is the solar degree and the decan, and the widget above will give you both from your own year and birthplace, along with the distance between your Sun and the nearest sign boundary. On 7 October that distance is large, which means the answer never depended on the details. The decan is the part of the report that carries information here, since the sign is common to everyone born across roughly a month and the band narrows that to about ten days.
Questions people ask about this
What sign and decan is 7 October?
Libra, in its second decan. The Sun sits near fourteen degrees, comfortably inside the band running from ten to twenty, in every year from 1930 to 2035.
Why is Saturn linked to part of a Venus ruled sign?
The Chaldean order distributes the seven traditional planets in a fixed sequence across all thirty six decans, running from the slowest to the fastest and repeating. It does not respect sign rulership, which is why a Venus sign contains a Saturn band.
Do both rulers apply at once?
In traditional practice, yes. The sign ruler describes the whole thirty degree stretch and the decan ruler colours the ten degree part of it. Readings combine them rather than choosing between them.
Is the decan the same as a decanate in other systems?
The divisions are the same ten degree bands, but the rulers differ. One common alternative assigns each decan the ruler of the sign of the same element, which gives a different planet from the Chaldean sequence for most bands.
Does the degree affect anything measurable?
It decides the exact aspects the Sun makes to other planets and, once a birth time is known, which house it falls in. Those are calculated from the longitude, so the sign name on its own is not enough for either.
Can two people born on 7 October have different Moons?
Yes. The Moon can cross a sign boundary at any hour, so a morning birth and an evening birth on the same date can carry Moons in adjacent signs.