Two planets that are usually contrasted
The Chaldean order runs rulers through the thirty six decans in a fixed sequence starting at Aries, and by the time it reaches the beginning of Sagittarius the sequence has arrived at Mercury. The sign itself is Jupiter's in every version of the tradition.
The two planets are conventionally set against each other. Jupiter is associated with the wide view and with what a thing means in general, and Mercury with the particular, with naming, sorting and arguing. Putting Mercury inside Jupiter's sign is therefore read as the sign's appetite for the general working through detail: teaching rather than travelling, or an argument built piece by piece toward a broad claim.
That is a convention carried down through the texts. It describes what the scheme says, not what a person is, and it should be weighed accordingly. A competing scheme based on element and sign order gives this band to Sagittarius itself and so to Jupiter twice over, and both are in circulation, which is why decan rulers quoted elsewhere may differ.
Where the Sun actually is
Taken at noon in every year from 1930 to 2035 the Sun on this date has stood between about two and four degrees of Sagittarius. That is safely inside the band, with no year in the span putting it back into Scorpio or forward past ten degrees.
The window stays this tight because the calendar is built to hold the date against the orbit. Three common years let the date creep forward relative to the Sun's progress and the February leap day returns it, so the figure oscillates within a small range instead of sliding. Inside a single day the Sun covers about one degree, far too little to move either the sign or the band.
What a low degree does and does not signify
It signifies position and nothing about strength. Membership of a sign is not graded, so a Sun at three degrees is inside Sagittarius exactly as fully as one at twenty three. What the figure genuinely governs is aspects, which are measured in degrees rather than in signs, and house placement once a birth time is known.
It also fixes the distance to the nearest boundary, which here is a few days back to the start of Sagittarius. Anyone who has been told Scorpio by one site and Sagittarius by another can settle that permanently: the disputed dates in this part of the calendar are the twenty first through the twenty third, and this is not one of them.
The forward edge is far off as well. Ten degrees of Sagittarius, the end of this band, is around a week of solar travel ahead, so neither the sign nor the band is in any doubt on this date in any year of the span.
The placements a date cannot supply
The Sun is slow enough for a calendar date to bracket it closely, which is the entire reason sun signs are quoted everywhere. Nothing else cooperates. The Moon travels roughly half a sign a day, so on this date it can be in either of two signs depending on the hour, with the pair changing from year to year.
The rising sign runs through all twelve within twenty four hours and depends on the latitude of the birthplace as well as the clock, and the twelve houses follow from it. The widget above takes a year, a time and a place and returns the exact solar degree in place of the century-wide window, the Moon and rising signs, and the distance from the birth to the nearest sign boundary.
Questions people ask about this
Which decan is 25 November?
The first decan of Sagittarius, the band from zero to ten degrees. The Chaldean order assigns it to Mercury, while the triplicity scheme leaves it with Jupiter.
Is 25 November always Sagittarius?
Yes. The boundary falls on 21, 22 or 23 November depending on the year, so this date is two to four days past it in every year checked.
What degree is the Sun on this date?
Between about two and four degrees of Sagittarius at noon across the last century. Your own year, hour and birthplace narrow that to a single figure.
Why do two schemes give different decan rulers?
Because they are built on different principles. The Chaldean order runs a fixed planetary sequence through all the decans, and the triplicity scheme assigns each to a sign of the same element.
Does Mercury in Jupiter's sign create a conflict?
The tradition reads it as a combination rather than a clash: the wide view pursued through detail. That is inherited convention and not a measurement of anything.
What should I check after this?
The Moon and the rising sign, since a calendar date cannot supply either. Both need a birth time and the rising sign needs the birthplace as well.