The range, 20 April to 20 May
The Sun enters Taurus at thirty degrees of ecliptic longitude, on 19 or 20 April, and leaves at sixty degrees on 20 or 21 May. Neither end has anything to do with a calendar month; both are positions on a circle.
Published tables differ by a day at each edge for a mechanical reason. Because a tropical year overshoots a calendar year by close to six hours, an ingress arrives later on the clock for three years running and is then thrown back by the leap day, so it moves within a window of about thirty six hours and never settles.
A season with no solstice or equinox in it
Taurus is one of the four fixed signs, and the fixed signs occupy the middles of the seasons rather than their turning points. The Sun spends the whole of Taurus between the March equinox and the June solstice, still climbing in declination but no longer at either extreme.
The old cross quarter day at the start of May falls near fifteen degrees of Taurus, the exact midpoint of the northern spring, and the festivals attached to that date across Europe are calendar folklore built on the same astronomical halfway mark. Whether they say anything about a person born then is not something the position itself decides.
What sidereal reckoning does to these dates
The sidereal zodiac used in Indian astrology is tied to the stars, and the equinox has crept backwards against those stars over the centuries at a rate that now amounts to about twenty four degrees. Sidereal Taurus therefore runs from around the middle of May to the middle of June.
A tropical Taurus Sun in the sign's first twenty four degrees is a sidereal Aries Sun. Both answers are correct within their own frame, and the disagreement is a difference of origin, not of arithmetic.
Narrower than the sign: the decans and the exaltation
The Moon's exaltation sits at three degrees of Taurus, so it falls within the first few days of the season and nowhere else. The decans then split the month into three: Mercury over the opening ten degrees, the Moon over the middle, Saturn over the last, which is a finer grouping of birthdays than the sign name alone provides.
A date will not give a Moon sign, since the Moon travels roughly half a sign in a day and needs a birth time to be pinned down, and it will not give an Ascendant at all without the place as well.
Questions people ask about this
What are the Taurus dates?
Approximately 20 April to 20 May. The exact start falls on 19 or 20 April and the end on 20 or 21 May, varying with the year and with the time zone the birth is dated in.
Why do the dates change from year to year?
Because the tropical year is not a whole number of days. The ingress slips about six hours later each year and is pulled back by each leap day, so it oscillates across roughly a day and a half.
When is Taurus season this year?
Within the range above, at a minute that has to be calculated for the specific year. Anyone born close to either edge needs the actual solar position rather than a table.
Why does Vedic astrology not make me Taurus?
It measures from the fixed stars rather than from the equinox, and the two references have separated by about twenty four degrees. That moves every sidereal boundary later by a little over three weeks.
Does being born on the first day of Taurus mean anything special?
It puts the Sun in the first degree of the sign, which matters for aspects and house placement. The tradition does not read it as a weaker or stronger version of the sign itself.