The position first
Checked at noon in every year from 1930 to 2035, the Sun on this date has fallen between roughly one and a half and three degrees of Leo. The band is narrow because the annual six hour drift is corrected by the leap day, so a fixed calendar date oscillates rather than slides.
Those degrees sit in the first face of Leo, the stretch from zero to ten. Leo itself is fixed fire and is ruled by the Sun in every scheme, ancient and modern, with no competing claim. The argument is entirely about the face. That is worth saying at the start, because a reader meeting Saturn on a Leo birthday page usually assumes the sign itself is in question.
What the Chaldean order says
The Chaldean sequence arranges the seven visible planets by apparent speed, from the slowest to the fastest, and walks that cycle through the thirty six faces beginning at zero degrees of Aries. Because thirty six divides by seven with a remainder, the assignment shifts steadily and no sign gets a tidy pattern. Counted out, the opening face of Leo arrives at Saturn.
Writers in this tradition read the band as Leo with an unexpected weight on it, warmth under constraint, display that has to be earned rather than assumed. Saturn is the coldest and slowest of the visible planets and the Sun is the hot centre of the scheme, so the pairing is deliberately awkward and the older texts do not smooth it over.
What the triplicity scheme says
The competing scheme gives the three faces of a sign to the three signs of its element in order. Leo is fire, and the fire signs run Aries, Leo, Sagittarius, so the faces of Leo go to Leo, Sagittarius and Aries. The first stays at home, which leaves the Sun ruling both the sign and its opening band.
Read this way the same degrees become the least diluted part of Leo rather than a constrained one, sign and face pointing at the same planet. Two respectable sources can therefore describe a 25 July Sun in almost opposite terms, one as constrained and one as unhindered, while making no error, which is why a page quoting one ruler without naming its scheme has withheld the important half.
Holding both without choosing
The reasonable position is that these are conventions rather than findings. Neither scheme can be checked against the sky, since both are ways of dividing a circle that was already divided, and no observation could ever separate them. What can be checked is the degree, and the degree is the same under either scheme.
So take the position as the fact and the two readings as commentary on it. The widget above returns your exact degree from your year, your hour and your birthplace, along with the distance to the nearest sign boundary, which on 25 July will come back at a day or two behind you on the Cancer side. From there both schemes are readable and neither has to be believed. That is the arrangement this site prefers wherever the older material contradicts itself, since presenting one branch as settled would be the easier route and the less accurate one.
Questions people ask about this
Which planet rules the first decan of Leo?
Saturn in the Chaldean face order and the Sun in the triplicity scheme. Both systems remain in use, and a source should say which one it is quoting.
Is 25 July always Leo?
Yes. Every year sampled at noon from 1930 to 2035 puts the Sun between roughly one and a half and three degrees of Leo, past the crossing at every hour.
Which decan scheme is correct?
Neither can be verified, because both are conventions for dividing a circle rather than observations. They are best treated as two readings of the same measured position.
Does a Saturn ruled decan mean hardship?
No. The tradition describes a tension between constraint and display, and this site does not treat any placement as good or bad fortune. A different scheme reads the same degrees as pure Leo.
What is the solar degree on 25 July?
Roughly one and a half to three degrees of Leo depending on the year. The widget above gives the exact figure from your own details.
Does the decan affect my Moon or rising sign?
No. Decans apply to any placement, but the one described here is the Sun's. Your Moon and ascendant have their own degrees and their own faces, and both need your birth time.