How much of Taurus is left
At noon in every year from 1930 to 2035, the Sun on 18 May has stood between about twenty six point six and twenty eight degrees of Taurus. A sign is thirty degrees wide and the Sun covers a little under one degree a day, so from that position there are two to three days of Taurus remaining.
That margin is wide enough that neither the hour of birth nor the time zone can change the sign. A birth at one minute past midnight and one at midnight the following night sit less than a degree apart, and both are inside Taurus by a comfortable distance.
Why late degrees get talked about
There is a habit in popular writing of treating the last part of a sign as weakened or as blending into the next, usually under the word cusp. Technically nothing supports that. At any instant the Sun has a single longitude and that longitude lies inside exactly one sign. A Sun at twenty seven degrees of Taurus is as much in Taurus as one at five.
Where the degree does matter is in aspects. Aspects are angular relationships measured in degrees, so a Sun at twenty seven of Taurus makes contacts to placements that a Sun at five would miss entirely. That is the real reason to know your degree, and it has nothing to do with blending.
The cusp idea is worth taking apart because it is repeated so widely. What the word usually marks is a gap in someone's information: a date range was consulted, the date sat near its edge, and no calculation was done. Once the year, the hour and the birthplace are supplied, the gap closes and there is nothing left to blend.
The decan at this point
Twenty seven degrees puts the Sun in the final decan of Taurus, from twenty to thirty. The Chaldean order gives that band to Saturn and the triplicity scheme, walking Taurus, Virgo and Capricorn, arrives at Capricorn and so at Saturn as well.
The tradition reads the Saturn third of Taurus as the most contained part of a Venus ruled sign: still attached to the tangible, but conservative about how much it will spend or commit. Taken as a whole, Taurus is fixed earth, read as sustaining and unhurried. Both of those are interpretations rather than measurements, and they are marked as such here.
What being near the end changes elsewhere
Nothing about the Moon or the horizon follows from the solar degree. The Moon moves about thirteen degrees a day and can change sign within any 18 May, leaving two candidates until the hour is known. The rising sign turns through the whole zodiac in a day and could be any of the twelve.
If you have been told you are on a cusp because your birthday is late in May, the widget above will report how far your birth actually fell from the Gemini boundary. For this date it will come back as a distance measured in days, which is a good deal more useful than the label.
House placements follow from the rising sign, so they are unavailable too, and with them the areas of life the tradition assigns to each planet. A birth date reaches one body out of ten or so and one layer out of several. That is worth having and it is not a chart.
Questions people ask about this
Is 18 May Taurus or Gemini?
Taurus, in all one hundred and six years sampled from 1930 to 2035 and at every hour. The Sun reaches Gemini about three days later, around 21 May.
Am I on the Taurus Gemini cusp?
No. A cusp describes missing information rather than a mixed state, and here nothing is missing. The Sun sits near twenty seven degrees of Taurus, several days short of the boundary.
Does a late degree weaken the sign?
Not in any technical sense. A Sun at twenty seven degrees is fully in Taurus. The degree affects which aspects the Sun makes, not whether the sign counts.
Which decan is this?
The third decan of Taurus, twenty to thirty degrees, ruled by Saturn in both the Chaldean and the triplicity schemes. The tradition reads it as the most reserved part of the sign.
Could my time zone put me in Gemini?
No. Time zones shift a birth by hours at most, and the Sun moves less than a degree a day, so the shift is a fraction of a degree against a margin of about three degrees.
What is still worth calculating?
The Moon sign, the rising sign and the houses, all of which need your birth time. Those carry the detail that separates your chart from everyone else born the same week.