The first degrees of the circle
Zero degrees of Aries is where the ecliptic and the celestial equator cross at the March equinox. It is the origin of the whole tropical measuring system, not just the start of a sign, and every other longitude is counted from it.
A 22 March birth falls one to two degrees past that origin. In most years the equinox has arrived two days earlier, so the Sun has covered a couple of degrees by noon on this date. The position has never wandered outside 0.9 to 2.3 degrees across the sampled century.
That origin point is also why the tropical zodiac and the constellations no longer line up. The crossing itself moves slowly against the stars, about a degree every seventy two years, so the sign called Aries and the stars called Aries have drifted apart over two thousand years. The tropical system measures from the crossing regardless, which is why the dates stay stable while the background does not.
Why a century barely moves it
The Sun's circuit takes about 365.2422 days and the calendar year takes 365, so each ordinary year ends with the Sun a quarter of a degree further along at the same hour. The leap day then removes almost exactly the accumulated surplus.
Over a hundred years the position on this date therefore oscillates inside a band about a degree and a half wide instead of drifting away. Which end of the band you sit on comes down to your position in the leap cycle. The widget above resolves that from your own year, and also reports how far your Sun was from the nearest sign boundary in degrees rather than in days.
The band and its ruler
Each sign splits into three decans of ten degrees, and the first decan of Aries runs from zero to ten. In the Chaldean scheme that band is assigned to Mars, which also rules the sign as a whole, so the decan doubles the sign's own ruler rather than modifying it.
Traditional writers treat that doubling as the most concentrated expression of the sign, Mars on Mars with nothing softening it. It is worth saying plainly that this is a statement about the band in the older texts and not a claim about anybody born inside it. The decan is a fact you can check. What the tradition reads into it is interpretation, and it is fair to hold the two to different standards.
It also has a small technical consequence. In several house systems a Sun at one or two degrees of a sign will often sit in the house before the one its sign suggests, depending on the birth time and latitude. That is another reason the degree is worth having and a date range is not.
What a date cannot tell you
The Moon travels roughly thirteen degrees a day, which means that on a given 22 March it may be in either of two signs and occasionally three. The date alone narrows it no further than that.
The Ascendant is untouched by the date. It cycles through all twelve signs each day, so it depends on the birth hour and the latitude of the birthplace. Two people born the same morning in different countries can share this Sun and share nothing else at the angles of the chart.
Mercury and Venus are the exception in the reader's favour. Both stay close to the Sun, so this date puts Mercury within about a sign of Aries and Venus within two, which is a genuine narrowing even though the exact degrees still need a year.
Questions people ask about this
Is 22 March Aries or Pisces?
Aries, in every year from 1930 to 2035 measured at noon. The equinox arrives on the twentieth in most recent years and on the twenty first at the far end of the range, so this date is always past it.
What degree is the Sun on 22 March?
Between about one and two degrees of Aries at noon, depending on where your year sits in the leap cycle. The widget above gives the exact figure for your year, hour and birthplace.
Which decan is this?
The first decan of Aries, zero to ten degrees, ruled by Mars in the Chaldean order. That is the same planet that rules the sign, so the sign ruler and the decan ruler agree here.
Is a very low degree a weak placement?
No. The first degree of a sign is as fully inside it as the fifteenth. Low degrees matter for aspect work and for house placement, and some traditional writers treat the opening degrees as a distinct case, but the sign itself is not diluted.
Does the equinox time affect my chart?
Only through the Sun's position, which it defines. Since this date falls comfortably after the crossing, the exact equinox hour changes your degree slightly and never changes your sign.
What else would I need for a full reading?
A birth time and a birthplace. Between them they fix the rising sign, the house cusps and the Moon's exact degree, none of which the calendar date supplies.