The centre of the sign
Across noon positions from 1930 to 2035, the Sun on 5 May sits between fourteen point one and fifteen point four degrees of Taurus. Fifteen degrees is the exact halfway mark, so this date brackets it, falling just short in most years and just past it in the latest.
Being at the centre means being as far from a sign boundary as a position can get, about fifteen degrees in either direction, or roughly a fortnight of solar motion. There is no boundary question here of any kind, in any year, at any hour. Whatever else a chart for this date holds, the sun sign is not among the uncertainties.
Why the midpoint was thought to matter
Older texts sometimes treat the middle degrees of the fixed signs as significant, since the fixed signs already sit at the centres of their seasons and the fifteenth degree is the centre of the centre. That is where a handful of prominent stars were traditionally located relative to the tropical framework, and where some systems place points they call the middle of the sign.
It is fair to record that as tradition and no more. The astronomical fact is simply that the Sun is halfway through a thirty degree arc. What any school makes of that is interpretation, and it varies considerably between them.
It is also worth saying that fixed stars move slowly against the tropical framework, so any claim tying a particular degree to a particular star holds for one era and not for all of them.
The decan and the two rulers
Fifteen degrees puts this birthday in the middle of the second decan of Taurus, the band from ten to twenty, and again at the centre of it rather than near an edge. The Chaldean order of faces gives that band to the Moon. The triplicity scheme, which shares the earth decans between Taurus, Virgo and Capricorn in turn, gives it to Virgo.
Both sit under Venus, the classical ruler of the whole sign. The tradition reads the sign as fixed earth, patient and attached to the tangible, and reads the second face as either steadying that further, in the lunar version, or making it more exacting, in the Virgo version. The disagreement is old and unresolved, so the useful thing is to know that it exists. A single named ruler presented without qualification has simply picked one tradition and left the other unmentioned.
What the date will not tell you
A birthday fixes the Sun and nothing else. The Moon travels about thirteen degrees a day and changes sign every two and a half days or so, which leaves a 5 May birth with two possible Moon signs until the hour is known. The rising sign has all twelve open, since the whole zodiac crosses the horizon daily and the rate varies with latitude.
Put in order of how much they distinguish one person from another, the sun sign comes last of the three. It is the part a date settles precisely and the part that separates you least. The widget above computes the exact degree for your own year and birthplace and reports the distance to the nearest sign boundary, which on this date is about as large as it gets. That is a useful thing to have confirmed even when the answer was never in doubt.
Questions people ask about this
What sign is 5 May?
Taurus, at noon in every year from 1930 to 2035. The Sun sits near fifteen degrees, the middle of the sign, so the answer does not depend on the year or the hour.
Why is the fifteenth degree significant?
Only by convention. It is the halfway point of a thirty degree sign, and some older schools attach meaning to the middle degrees of the fixed signs. The astronomy is just a position.
Which decan is a 5 May birthday?
The second decan of Taurus, ten to twenty degrees, and near the centre of it. The Chaldean order gives that band to the Moon and the triplicity scheme gives it to Virgo.
Can a 5 May birth ever be Aries or Gemini?
No. Both boundaries are about fifteen degrees away, which is around a fortnight of solar motion. No plausible calculation produces either answer.
Does being mid sign make the sun sign stronger?
Not technically. A Sun at one degree is as much in the sign as a Sun at fifteen. The degree affects aspects and house placement rather than whether the sign counts.
What still needs my birth time?
The Moon sign, which has two candidates on this date, and the rising sign, which has twelve. Both are usually more distinguishing than the Sun.