The range across a century
Measured at noon in each year from 1930 to 2035, the Sun on 24 April sat between roughly three and a half and five degrees of Taurus. Four degrees serves as the figure. That is the entire spread over more than a hundred years, not an average with outliers hidden behind it.
Set against the way birthdays are usually described, that is a much sharper statement. A sign covers thirty degrees and about a month. A degree figure this stable narrows the position to a few days' worth of solar motion and does so for any birth year you care to name.
The mechanism, step by step
The tropical year is about three hundred and sixty five and a quarter days. A common calendar year is a quarter of a day short of that, so the Sun reaches a given longitude roughly six hours later by the clock in each successive common year, and the position on a fixed date creeps backwards.
Every fourth February gains a day, which pushes the position forward again by about eighteen hours in a single step. Over the four year cycle the creep and the correction very nearly cancel, leaving a small sawtooth rather than a drift. Skipping the leap day in years like 1900 and 2100 stops even the sawtooth from accumulating across centuries.
The residual sawtooth is what the degree and a half of spread actually is. Within a four year cycle the position on this date is at its earliest just before a leap day and at its latest just after one, and the difference between those two extremes is most of the range quoted above.
Why the figure is worth having
Four degrees of Taurus falls in the first face of the sign, the band from zero to ten degrees, which the Chaldean order gives to Mercury and the triplicity scheme gives to Venus. Knowing the degree is what lets you place the face, and the face is the layer that separates one Taurus birthday from another.
It also tells you how much margin you have. Four degrees past the boundary is about four days, which is far more than the year to year drift in the crossing, so the sign is not in doubt at any hour. On dates where the margin is a few hours instead, the same figure is what shows that the answer needs the birth time.
What stays variable
Only the Sun behaves this way on a fixed date. The Moon covers about thirteen degrees a day and can be in either of two signs within a single 24 April, and in any of the twelve across different years. The ascendant runs through the entire zodiac between one midnight and the next.
So a date buys one stable placement and no others. The widget above asks for the year, the hour and the birthplace precisely because those are what the calendar cannot carry, and it returns the exact degree along with the distance from the nearest sign boundary.
Questions people ask about this
Is 24 April always Taurus?
Yes. Every year from 1930 to 2035 checked at noon puts the Sun in Taurus on this date, about four degrees past the boundary, which is roughly four days of margin.
Why does the solar degree barely change?
Because the calendar and the orbit stay in step. The Sun arrives about six hours later each common year and a leap February pulls it back by about a day, so the two effects cancel over the cycle.
How wide is the variation?
About a degree and a half across the sampled century, from roughly three and a half to five degrees of Taurus. Your own figure depends on your year, hour and birthplace.
What decan is four degrees of Taurus?
The first, covering zero to ten degrees. The Chaldean face order gives it to Mercury and the triplicity scheme gives it to Venus, which also rules the sign.
Does the same stability apply to my Moon?
No. The Moon moves about thirteen degrees a day, so on the same calendar date in different years it can be anywhere in the zodiac. Only the Sun is pinned by the date.
Will the figure hold for births after 2035?
It holds while the current leap rules stand, which is why the century exceptions exist. The drift over a few more decades is small compared with the degree and a half already quoted.