The decan, not the sign, is the interesting layer
Signs are thirty degrees wide and a birthday tells you which one you are in. Decans divide each sign into three bands of ten, giving thirty six across the zodiac, and they are old: the system descends from Egyptian star lists that predate much of the sign lore built on top of it.
At noon across 1930 to 2035, a 1 February Sun has fallen between 11.5 and 12.9 degrees of Aquarius. That is squarely in the second decan, ten to twenty degrees, with well over a degree of clearance at either end. No year in that span puts it anywhere else.
Decans matter more in some traditions than others. Hellenistic and medieval work uses them routinely, often under the name faces, as one of the minor dignities a planet can hold. Much modern popular astrology drops them entirely, which is why a reader can go a long way into the subject without meeting the idea at all.
Both schemes name Mercury
The Chaldean order runs its rulers in a fixed sequence, Mars, Sun, Venus, Mercury, Moon, Saturn, Jupiter, starting at zero degrees of Aries and repeating through all thirty six decans. Counting round, the second decan of Aquarius takes Mercury.
The triplicity scheme works from the elements instead. Aquarius is the second air sign in order, so its decans are handed to the air signs beginning from the second, which puts Gemini in charge of this band. Gemini is also a Mercury sign, so both schemes arrive at the same planet by unrelated routes. That agreement is uncommon, and it is why this stretch of Aquarius is described more consistently than most.
What the tradition reads into it
Aquarius is fixed air, given to Saturn in the older rulership and to Uranus since the modern one took hold. The tradition reads it as a sign of systems and of a certain deliberate distance from what it observes.
Mercury over the second decan is read as tilting that toward language, classification and explanation, so the abstraction gets a means of being communicated rather than simply held. That is an interpretation carried by the tradition, not a measurement, and how much weight it deserves is a matter of judgement. The degree itself is a measurement and is the part this page can state without qualification.
One practical point about the band itself: because it runs from ten to twenty degrees and the Sun covers roughly a degree a day, the whole second decan of Aquarius corresponds to about ten calendar days, from around the end of January to around the tenth of February. A birthday anywhere in that stretch shares this decan.
Where the date runs out
The Sun is one placement. On 1 February the Moon has stood in every sign of the zodiac across different years, and within any single year it may change sign partway through the day, so the hour matters. The rising sign is decided almost entirely by the minute and the latitude of birth, since the full zodiac rises in about twenty four hours.
The widget above takes your year, hour and birthplace and returns your actual solar degree along with the distance to the nearest sign boundary. On this date that distance is comfortable, which is itself worth knowing.
None of that is a reason to distrust the sun sign. It is accurate and it is checkable. It is simply narrow, and a page that presents it as the whole picture is overselling one placement.
Questions people ask about this
Is 1 February always Aquarius?
Yes. The Sun enters Aquarius around 20 January and leaves around 18 February, so this date sits near the middle with plenty of margin. No year moves it.
What decan is a 1 February birthday?
The second decan of Aquarius, running from ten to twenty degrees. The noon degree on this date has stayed between about 11.5 and 12.9 for the whole of the last century.
Why do the Chaldean and triplicity schemes agree here?
By coincidence of counting. The Chaldean sequence lands on Mercury for this decan, and the triplicity scheme assigns it to Gemini, which Mercury also rules. Most decans get different answers from the two.
Does the decan change my sun sign reading?
It refines it rather than replacing it. The tradition treats the decan as a shading within the sign, so an Aquarius here is read as Aquarius with a Mercury inflection.
How precise is the degree without a birth time?
Within about half a degree. The Sun moves roughly one degree a day, so assuming noon can only be out by half a day's motion, which never affects the sign or, on this date, the decan.
Are decan meanings the same everywhere online?
Not reliably. Many articles use the triplicity scheme without naming it, so a ruler quoted elsewhere can differ from the Chaldean one. On this decan the two happen to coincide.