The centre of a cardinal sign
Each sign spans thirty degrees, so the fifteenth degree is its middle. In cardinal signs, meaning Aries, Cancer, Libra and Capricorn, that middle point has been treated as significant since antiquity because it stands a quarter turn from the middles of the others.
Those four midpoints are sometimes grouped together in older material and given collective attention. The reason is geometric rather than mystical: bodies at fifteen degrees of the cardinal signs form exact squares and oppositions with one another, so a planet there is aspected by anything sitting at the same degree of the other three.
Popular writing tends to skip that and offer a mood instead. The geometry is the more useful half, because it can be checked on any chart wheel.
What the position is on this date
Taken at noon from 1930 to 2035, the Sun on 5 April has fallen between about fourteen and three quarters and sixteen and a quarter degrees of Aries. The spread is small because each leap day cancels the drift accumulated over the previous three years, which keeps the calendar and the orbit in step.
Anyone born in the small hours will be a fraction under the noon figure and anyone born late in the evening a fraction over, since the Sun covers roughly one degree a day. That variation is far too small to move the sign or the ten degree band.
Sitting in the middle of the solar band
The band from ten to twenty degrees of Aries is the second of the sign's three, and the Chaldean order assigns it to the Sun. Fifteen degrees is its exact centre, so this birthday is as deep inside a decan as it is possible to be.
Where a position near a band edge can reasonably be read with an eye on the neighbouring band, this one cannot. Whatever the tradition attaches to a solar decan inside a Mars sign applies here without qualification: the drive of Aries turned toward visibility and toward being the one who carries a thing rather than the one who begins it. That is a convention handed down through the texts, and it should be read as such rather than as a finding.
None of it makes the position stronger or weaker than a neighbouring one. It simply removes ambiguity about which band applies.
What the midpoint does not decide
A precise solar degree still describes one body. The Moon crosses about half a sign a day, so on 5 April it is often in one sign at breakfast and the next by bedtime, and no birthday page can tell you which applies.
The Ascendant turns through the whole zodiac in twenty four hours and depends on latitude as well as clock time. The widget above computes the exact solar degree for a year and place, the Moon and rising signs from a birth time, and the distance from the birth to the nearest sign boundary.
Being at the middle of a sign is worth knowing mostly because it is unambiguous. It removes any argument about the sign and any argument about the band, which leaves the rest of the chart as the only place where an actual question remains.
Questions people ask about this
What is special about fifteen degrees?
It is the exact centre of a sign, and in the cardinal signs those centres sit at right angles to each other. A planet there forms exact aspects with anything at fifteen degrees of Cancer, Libra or Capricorn.
Is 5 April always Aries?
Yes. The Sun is around the middle of the sign, roughly two weeks after the equinox and two weeks before the move into Taurus, so no year or birth time puts it elsewhere.
Which decan is this?
The second decan of Aries, from ten to twenty degrees, and the position sits at its centre. The Chaldean order assigns that band to the Sun.
Does being mid sign make a sun sign stronger?
Not in any technical sense. A Sun at fifteen degrees is exactly as much in Aries as one at one degree. The degree matters for aspects and house placement rather than for membership.
How precise is the degree given here?
It is a window of about a degree and a half across the last century, taken at noon. Your own year and hour narrow it to a single figure, which the widget above will return.
Do I still need a birth time?
For the Sun, no. For the Moon, usually yes, since it can change sign during the day. For the rising sign and the houses, always.