The one thing the date settles
On 20 September the Sun stands between 26.6 and 28.0 degrees of Virgo at noon, taken across every year from 1930 to 2035. It is late in the sign, in the third decan, and several days short of the equinox that opens Libra. No hour of the day and no birthplace changes that conclusion.
The Sun can be pinned this way because it is slow. It covers about a degree a day, so a whole day of uncertainty about the birth time costs you a single degree. That tolerance is what makes sun sign tables possible in the first place, and it is also why they say so little.
That is also why sun sign columns exist at all and why nothing comparable exists for the Moon. A newspaper can print twelve solar paragraphs and be right about the sign for every reader. It could not do the same for any faster placement without asking for a birth time first.
The Moon has two answers
The Moon moves roughly thirteen degrees a day, thirteen times the solar rate, and completes a sign in about two and a quarter days. Any calendar date therefore contains a sign change fairly often, and even when it does not, adjacent dates differ.
In practice a birth on 20 September has one of two possible Moon signs in most years, decided by the hour and, where the change falls near midnight locally, by the birthplace as well. Since the Moon carries the emotional and habitual layer in traditional reading, this is not a footnote. Two people born on the same date can differ on it entirely.
Where the change falls close to local midnight, the birthplace matters as well as the hour, because a lunar ingress is a single global instant and only the clock reading differs. A birth at eleven at night in Chicago and one at the same clock time in Berlin are hours apart in absolute terms.
The rising sign has twelve
The Ascendant is the point of the ecliptic coming over the eastern horizon at the moment of birth. The Earth turns once a day, so the whole zodiac rises in twenty four hours and the Ascendant changes about every two hours. A date on its own excludes none of the twelve.
The Ascendant also sets the houses, which is where a chart stops being a list of signs and starts describing areas of life. Without a birth time that entire structure is unavailable. This is why a birthday page can never substitute for a chart, and why the honest version of one says so.
What to do with an unknown birth time
If the hour is missing, the usual convention is to calculate for noon and to treat the fast moving placements as provisional. On this date that convention is safe for the Sun, since noon and midnight give effectively the same answer for the sign and differ by half a degree at most.
For the rest, the widget above will show which placements are stable across the whole day and which flip. Anything that changes depending on the hour should be marked unknown rather than guessed, and the fastest moving points should be treated as unavailable until a birth record turns up.
For the record, this date is in the third decan of Virgo, the band from 20 to 30 degrees, in every year of the range. The Chaldean scheme gives that band to Mercury, which also rules the sign, while the triplicity scheme calls it the Taurus decan under Venus.
Questions people ask about this
Is 20 September Virgo or Libra?
Virgo, in every year covered here. The equinox that starts Libra falls on the twenty second or twenty third, so this date sits comfortably inside Virgo with no year dependence.
What is my Moon sign if I was born on 20 September?
It depends on the hour and usually has two possibilities in any given year. The Moon spends only a couple of days in each sign, so the date alone cannot choose between them.
Can I find my rising sign without a birth time?
Not exactly. You can narrow it by working backwards from events or by testing which houses make sense of known facts, but any of the twelve is possible from the date alone.
How far into Virgo is this date?
Between 26.6 and 28.0 degrees, so roughly the last tenth of the sign. That places it in the third decan with a couple of degrees still to run.
Does being late in a sign mean anything?
Traditionally the late degrees of a sign are sometimes read as the sign's qualities at their most developed. It is a reading rather than a measurement, and it does not affect whether the sign applies.
Why does the degree vary at all between years?
Because a calendar year and an orbital year are not the same length. The mismatch pushes the Sun's position later within each four year cycle, and the leap day resets it, so the figure oscillates in a small range.