The one thing the date pins down
Because the Earth returns to nearly the same point in its orbit on a given calendar date each year, the Sun's ecliptic longitude on 28 August is close to repeatable. Measured at noon it has run between about 4.2 and 5.6 degrees of Virgo across the whole stretch from 1930 to 2035.
The leap year rule is what keeps it there. Left alone, a fixed date would slide against the seasons, and the extra day every fourth February hauls it back. The result is a small oscillation instead of a drift, which is why the fifth degree of Virgo is a reliable answer for this birthday across living memory.
The Moon, narrowed to two
The Moon covers roughly thirteen degrees of the zodiac each day, a little under half a sign. Over a single date it therefore occupies one sign, or crosses from one into the next partway through. Anyone born on 28 August has a Moon in one of two signs, and which two depends entirely on the year.
That is a real constraint, but it is not an answer. It also cannot be looked up from the date alone, since the pair of candidate signs changes from year to year as the Moon's cycle of roughly twenty seven and a third days runs out of step with the calendar month.
The Ascendant, narrowed to nothing
The rising sign is set by the Earth's rotation rather than its orbit. The complete zodiac passes the eastern horizon in a day, so any of the twelve signs can be rising on 28 August, and the sign changes on average every two hours. Four minutes of clock error moves the Ascendant by about a degree.
Everything that follows from the Ascendant is equally open. House cusps, and therefore which area of life each planet is read in, are undetermined by the date. A chart drawn without a birth time is missing its whole frame, which is why practitioners treat an untimed chart as a partial document.
Where the fifth degree does count
None of this makes the solar position pointless. Five degrees of Virgo is a specific place, and in traditional practice a specific place is what aspects are measured from. Anything sitting near five degrees of Pisces opposes it, near five degrees of Gemini or Sagittarius squares it, and those relationships hold whatever the birth time was.
It also fixes the face. Five degrees is halfway through Virgo's opening decan, the band from the start of the sign to ten degrees, which the Chaldean order assigns to the Sun and the triplicity order assigns to Mercury by way of Virgo. Both readings are old and both are interpretation, but they attach to a measured position rather than to a calendar box.
Trines, squares and oppositions taken from that point are the part of a chart that survives an unknown birth time, which is why an untimed chart is worth drawing at all. It is partial rather than empty.
The distinction worth holding on to is between what was measured and what was inferred. The degree and the face are measured. Everything a tradition reads into them is a separate matter, and should be presented that way.
Questions people ask about this
Is 28 August definitely Virgo?
Yes. Every year from 1930 to 2035 places the Sun in Virgo on this date at noon, and the boundary with Leo is several days behind. No hour or time zone changes it.
How much does the date tell me about my chart?
Less than most people assume. It gives the solar degree to within about a degree and the decan, and it narrows the Moon to two possible signs. It says nothing at all about the Ascendant or the houses.
What decan is a 28 August Sun in?
Virgo's first face, the opening ten degrees, with the Sun near the middle of it. The Chaldean scheme rules that face by the Sun and the triplicity scheme by Mercury.
Can I get a useful reading without a birth time?
Partly. The solar degree and the aspects to it are firm, and the Moon can often be pinned down if you can narrow the hour at all. The Ascendant and houses remain guesswork until a time surfaces.
Why do two people born the same day differ so much?
Because only the Sun is shared. Born twelve hours apart, two people can have Moons in different signs, opposite Ascendants and every planet in a different house, which is most of what a chart consists of.
What is my exact degree?
It falls between roughly 4.2 and 5.6 degrees of Virgo. The widget above narrows it to minutes of arc from your year, hour and birthplace, and reports the distance to the nearest sign boundary.