A settled date next to an unsettled one
Taken at noon across that century the Sun on 20 November has fallen between about twenty seven and twenty eight and a half degrees of Scorpio. Sagittarius opens at thirty, so even the highest figure in the span leaves around a day and a half of solar travel in hand, and the Sun covers only about a degree in a full day.
The following date is a different matter. There the ingress can arrive late in the evening, so the answer depends on both the year and the hour, and by the twenty second the two signs are close to evenly split across the span. That is why this date is the natural place to stop and state something flatly.
Why the boundary wanders at all
The Sun enters Sagittarius when it reaches two hundred and forty degrees of ecliptic longitude, which is one global instant rather than a calendar day. Because the tropical year runs about a quarter of a day longer than a common year, that instant arrives roughly six hours later each year, and the leap day in February pulls it back by nearly a full day.
The result is a boundary that oscillates across two or three dates in a four year cycle. Time zone plays a part as well: an ingress at two in the morning in London is still the previous evening in Los Angeles, so the calendar date of the crossing depends on where the birth happened. None of that reaches back as far as the twentieth, but it explains why the tables downstream disagree.
This is also the whole content of cusp talk. At any instant the Sun sits at one longitude inside one sign, so there is no blended state to occupy. The word describes a gap in someone's information rather than a condition in the sky.
What being at the end of a sign means
Almost nothing, technically. Membership of a sign is not graded, so a Sun at twenty eight degrees is in Scorpio as fully as one at eight. What the high degree does affect is which placements it aspects, since those are measured in degrees, and where it falls among the houses once a birth time is known.
The position sits in the closing ten degree band of the sign, which the Chaldean order assigns to Venus and the triplicity scheme assigns to Cancer and so to the Moon. Both schemes are in use, which is why decan rulers quoted in different places conflict. The reading handed down for either version is a matter of inherited convention rather than measurement.
The same applies to the previous boundary. Scorpio opened around 23 October, so this date sits roughly four weeks into the sign, which is why the only edge worth measuring against is the one ahead.
The rest of the chart, which the date does not touch
The Moon travels about half a sign each day, so two people born on this date some hours apart can have different Moon signs, and which pair is available changes from year to year. The rising sign moves through all twelve within twenty four hours and depends on the latitude of the birthplace as well as the clock, which is why it cannot be inferred from a date under any circumstances.
The widget above takes a year, a time and a birthplace, returns the exact solar degree instead of the century-wide window, and reports how far the birth fell from the nearest sign boundary. On this date the answer will come back with room to spare, which is not something the next few dates in the calendar can promise.
Questions people ask about this
Is 20 November Scorpio or Sagittarius?
Scorpio, at noon in every year from 1930 to 2035. The Sun is around twenty eight degrees along, which leaves roughly a day and a half of travel before the boundary.
Could an evening birth on this date be Sagittarius?
Not within the span checked here. The Sun covers about a degree in a full day, so even a birth just before midnight stays short of thirty degrees of Scorpio.
When does Sagittarius actually begin?
When the Sun reaches two hundred and forty degrees of longitude, which falls on 21, 22 or 23 November depending on the year and on the time zone of the birth.
What degree is the Sun on 20 November?
Between about twenty seven and twenty eight and a half degrees of Scorpio at noon across the last century. Your own year narrows that to one figure.
Am I on a cusp?
No, and there is no such placement in any case. The Sun occupies one longitude at any instant and that longitude lies inside a single sign. Cusp language describes missing information.
Which decan is this?
The final band of Scorpio, from twenty to thirty degrees, given to Venus by the Chaldean order and to the Moon by the triplicity scheme.