Decans, and where this date falls
A decan is a ten degree third of a sign, giving thirty six across the zodiac. The system predates the signs in some respects and comes from Egyptian star lists that were later folded into Greek practice.
Across noon positions from 1930 to 2035 the Sun on 8 March stands between about 17.0 and 18.4 degrees of Pisces. Both ends of that range sit inside the middle decan, which runs from ten to twenty, so this birthday belongs to that face in every year without exception.
The reason the range is so tight is the leap day. A calendar year falls about a quarter of a day short of the orbit, so the date drifts later by roughly six hours a year until February gains a day and pulls it back. Across a century the drift never accumulates into anything larger.
Two rulers, from two schemes
The Chaldean order runs Mars, Sun, Venus, Mercury, Moon, Saturn and Jupiter in a loop that begins at zero degrees of Aries and never restarts. Counting through, the middle face of Pisces lands on Jupiter, the older ruler of Pisces itself.
The triplicity scheme works from the element. The water signs run Cancer, Scorpio, Pisces, and a Pisces sequence takes them as Pisces, Cancer, Scorpio, so this face goes to Cancer and to the Moon. The schemes disagree here, and both are shown so the difference is visible rather than hidden.
What the tradition reads into it
Jupiter over a Moon face is traditionally read as receptive and expansive at once, inclined to take a situation in whole rather than in parts. Older texts also treat this stretch as the softest of the Pisces faces, with less of the sharpness the final one is given.
All of that is interpretation. It describes what the tradition attaches to a band of longitude, not a trait the calendar confers on anyone. What is checkable is the degree, and that is what the widget above returns.
Practitioners who use decans treat them as a modifier rather than a foundation. A Sun in the middle of Pisces is read first as Pisces and only then as coloured by the face, in the same way a degree is read after a sign rather than instead of one.
Everything the date does not fix
Two people born on 8 March in the same year, hours apart, share a Sun to within a fraction of a degree and can share almost nothing else. The Moon may have changed sign between the births. The Ascendant almost certainly has, since it moves through a new sign roughly every couple of hours.
That is the honest version of what a birthday tells you. It settles the Sun, which is one placement, and it leaves the rest to the hour and the place. The widget above also reports how far your Sun stood from the nearest sign boundary, which on this date is a comfortable distance.
Knowing the degree is still worth the minute it takes. It decides which face applies, it decides which aspects to other planets are close enough to count, and it settles whether any of the boundary arguments people have about birthdays apply to yours. On this date they do not.
Questions people ask about this
What decan is 8 March in?
The second decan of Pisces, the band from ten to twenty degrees. The date sits near the middle of it, so no year or birth hour moves it out.
Who rules that decan?
Jupiter under the Chaldean order and the Moon by way of Cancer under the triplicity scheme. The two schemes reach different planets here, which is common across the thirty six faces.
What is my solar degree if I was born on 8 March?
Somewhere between about seventeen and eighteen and a half degrees of Pisces at noon. The widget above narrows it further using your birth year, hour and place.
Is 8 March ever Aquarius or Aries?
No. Both boundaries are well over a week away in either direction, so this date is Pisces in every year on record.
Do decans matter as much as signs?
They are a second order refinement rather than a foundation. Practitioners who use them treat the decan as a modifier of the sign, not as a replacement for it.
Can two people born on 8 March have different charts?
Almost always. The Sun will match closely, but the Moon can differ by sign and the rising sign usually does, because it turns through the whole zodiac in a single day.