Why the sign is easy and uninformative
Virgo occupies thirty degrees of the ecliptic and the Sun takes about thirty days to cross it. That means roughly one birthday in twelve is Virgo and every one of them gets the same three or four adjectives from the same sources.
On 17 September the sign is beyond question. The Sun does not reach Libra until around 22 or 23 September, and the exact instant of that crossing wanders by a few hours from year to year, never by five or six days. So a page can state the sign confidently, and having done so it has said something true about millions of people and nothing about any of them.
The measurement underneath
At noon on this date the Sun has stood between about twenty three and seven tenths degrees of Virgo and roughly twenty five and a tenth, across every year from 1930 to 2035. The reason the figure hardly moves is structural. The calendar year is a quarter of a day short, so the date creeps forward against the Sun for three years, and then February gains a day and the creep is undone.
Your own degree sits somewhere in that range depending on your birth year, and then shifts a little further with the hour, since the Sun advances close to a degree in a day, and with the birthplace, because that is what converts your local clock time to a universal instant. The widget above does the conversion and returns the longitude directly.
The band that actually distinguishes birthdays
Twenty four degrees places this birthday firmly in the last of Virgo's three ten degree divisions. The divisions are Egyptian in origin, where thirty six star groups marked the hours of the night, and the planetary rulers were attached much later.
The Chaldean count gives this band to Mercury, the ruler of Virgo itself, and traditional writers describe it as the sign undiluted, weighted towards analysis and correction. The triplicity method gives it to Saturn instead and produces a more reserved description of the same ten degrees. Both are conventions. What is not conventional is which band your Sun fell in, and that is a matter of arithmetic. Almost no birthday page mentions the layer at all, which is why they all end up saying the same thing.
Where the real differences live
Even the decan is shared with everyone born in the same ten day stretch. The placements that separate individual charts are the ones a date cannot supply. The Moon has two candidate signs on this birthday and sometimes three, decided by the hour. The rising sign has all twelve, decided by the hour and the latitude of the birthplace together.
Once the rising sign is known the houses follow, and with them the question of where in a life each planet is read as operating. That is the level at which two people born on the same 17 September stop resembling each other. The sun sign is the entry point, not the description, and treating it as the description is the mistake nearly every page about this date makes.
Questions people ask about this
Is 17 September always Virgo?
Yes. The Sun leaves Virgo around 22 or 23 September, five or six days later, and that crossing moves only by hours between years.
What is the solar degree on 17 September?
Between roughly twenty three and seven tenths and twenty five and a tenth degrees of Virgo at noon, over the last century. The widget above gives your own figure.
Which decan is 17 September in?
The third decan of Virgo, from twenty to thirty degrees. The Chaldean order assigns it to Mercury and the triplicity scheme assigns it to Saturn.
Why do most birthday pages say so little?
Because they work from date ranges rather than from a calculation. A range gives the sign and stops, so the degree and the decan never appear.
Does knowing my degree change anything practical?
It decides which decan applies and which aspects the Sun makes to other planets, and once a birth time is known it decides the house the Sun occupies.
What should I look up after the sun sign?
The Moon sign and the rising sign. Both need a birth time, and between them they carry most of what makes one chart different from another with the same Sun.