One instant, twenty four local dates
An ingress is not a local event. The Sun reaches one hundred and eighty degrees of ecliptic longitude at a single moment, and every place on Earth experiences that moment simultaneously while reading a different time off the wall. When Libra begins at 02:00 UTC on 23 September, it is ten in the evening of the twenty second in New York and seven in the evening in Los Angeles.
This is why an American can be born on a date that a British table calls Virgo and be Libra all the same, and why a European born on what looks like a safely Libra morning may be reading a table written for a different meridian. Failing to convert the birthplace into the same frame as the ingress is the ordinary source of wrongly reported sun signs, far more often than any dispute about the astronomy.
Why the boundary moves in the first place
The tropical year is about a quarter of a day longer than the calendar year, so each ingress falls roughly six hours later on the clock than it did in the previous year, and then springs back about eighteen hours when February gains its extra day. Traced through a decade, the Virgo to Libra boundary wanders over about a day and a half.
Twenty four September sits far enough past the middle of that band that the drift never reaches it at noon. That is a stronger statement than most boundary dates can support, and it is worth stating plainly: on this date the year is not the variable. The hour and the place are what remain, and only for births close to midnight in the western hemisphere.
Virgo and Libra are less alike than a blend would suggest
Virgo is mutable earth ruled by Mercury, read as discriminating, practical and inclined to fix what is in front of it. Libra is cardinal air ruled by Venus, read as comparative, social and concerned with proportion. Both are described as fussy, which is where people notice a resemblance, but they are fussy about different things. Virgo attends to whether something works and Libra to whether something is fair or well proportioned.
No chart holds both from the Sun. At any instant the Sun sits at one longitude, inside one sign, so a birth a few minutes before the equinox point is completely Virgo and one a few minutes after is completely Libra. There is no transitional band and nothing is shared across the line. When someone says they are a Virgo Libra cusp, what they have is an unfinished calculation.
What follows if the answer surprises you
Very little, in truth. The Sun is one placement among ten or so that a chart is normally read from, and none of the others move because of this boundary. Your Moon, your Ascendant, Mercury, Venus and the rest are determined by the same birth moment and are entirely unaffected by which side of one hundred and eighty degrees the Sun had reached.
Note too that the signs are not all the same length in time. The Sun crosses Libra in a little over thirty days, against about twenty nine and a half near early January when the Earth is closest to the Sun and moving fastest, and about thirty one and a half through Cancer in July. That is why some boundaries in the year drift more visibly than others. The widget above handles all of it, taking your year, hour and birthplace and reporting how many hours from the boundary you were born.
Questions people ask about this
Is 24 September Virgo or Libra?
Libra. Taken at noon, every year from 1930 to 2035 has the Sun in Libra on this date, so the birth year does not change the answer. Only an extreme time zone case is worth a second look.
Why do some tables still print Virgo for 24 September?
Because they carry a fixed range that was rounded at some point and then copied. The Virgo to Libra boundary really does move across 22 and 23 September, and a table that stretches Virgo to the twenty fourth is simply generous with its rounding.
How does the birthplace change a sun sign?
It does not change where the Sun was, only which local date and hour that moment corresponds to. Since the ingress is one global instant, a birth in the Americas can carry a calendar date a day behind the one used in a European table.
Is there a Virgo Libra cusp?
No. The Sun occupies a single ecliptic longitude at any moment and that longitude falls inside one sign. Cusp is a word people reach for when the year, the hour or the place has not been established.
Does the autumn equinox always fall on the same day?
No. It has fallen on 22 and 23 September within the last century, moving later within each four year cycle and jumping back at each leap day. That is the same drift that makes fixed date ranges unreliable.
I was born close to the boundary. Does my Libra Sun still count?
Fully. A Sun at the first degree of Libra is as much in Libra as one at the twentieth. Nearness to a boundary affects aspects and house placement, not whether the sign applies to you.