How much of the sign is left
At noon in every year from 1930 to 2035, the Sun on 20 July stood between roughly twenty six and three quarters and twenty eight and a quarter degrees of Cancer. Since the sign ends at thirty, that leaves between about two and three degrees, or two to three days, before the Leo ingress.
Two days is a margin, not a coin toss. The Sun moves a little under a degree a day, so even a birth at one minute past midnight or one minute to it shifts the noon figure by less than half a degree. Nothing about the hour brings Leo into range on this date, and nothing about the time zone does either. A birth in Sydney and one in Vancouver on the same calendar date land at different degrees and the same sign.
Where the confusion comes from
Printed date ranges usually give Cancer as ending on 22 July, which puts 20 July within a couple of days of the stated end. Proximity on a calendar reads as proximity to doubt, and readers reasonably conclude they are on the edge of something. The ranges themselves are approximations of a moving instant, which does not help.
The genuinely divided dates here are 22 and 23 July, where the crossing actually falls and where the year and the hour decide the answer. This date is two steps back from that. It has the appearance of a boundary case and none of the substance of one. The distinction is easy to check and almost never made, so the word cusp keeps being applied to dates that do not need it.
What late degrees do and do not mean
A Sun at twenty seven degrees of Cancer is as fully in Cancer as one at three. Signs are not stronger in the middle and weaker at the edges, whatever the language of cusps implies. The degree matters for other reasons: aspects are measured with a few degrees of tolerance, house cusps fall at specific degrees, and progressed positions move outward from wherever the Sun began.
The one practical consequence of a late degree is that a progressed Sun changes sign relatively early in life, entering Leo after roughly two or three years by the common day for a year convention. That is a technique with its own assumptions and it is worth naming as such rather than presenting as a fact about you. Progressions are a symbolic timing method, not a second birth chart.
Settling it for your own birth
The figures above are noon values across a century, which is as precise as a page addressed to everyone can be. Your own position depends on the hour and on where in the world the clock was running, and it will land somewhere inside that band rather than at its midpoint.
The widget above computes it and reports your exact distance from the nearest sign boundary in degrees. For this date that reading will come back at a couple of degrees on the Leo side, which is the clearest available answer to anyone who has told you that you are half one sign and half the other. The Sun holds one longitude at a time, and a longitude falls inside exactly one sign.
Questions people ask about this
Is 20 July on the Cancer Leo cusp?
No. The Sun is around two to three degrees short of Leo, which is two to three days. The genuinely divided dates are 22 and 23 July.
Could a late evening birth on 20 July be Leo?
No. Twelve hours moves the Sun less than half a degree, and there are at least two degrees of Cancer left in every year sampled.
Does being late in a sign weaken it?
Not in any technical sense. A Sun at twenty seven degrees of Cancer is as much in Cancer as one at seven. Degree affects aspects and timing, not membership.
Why do the printed ranges say Cancer ends on 22 July?
Because a range has to round a moving instant to a whole day. The ingress drifts by up to a day and a half between years, so the boundary date itself varies.
What decan does 20 July fall in?
The third of Cancer, from twenty to thirty degrees, ruled by the Moon in the Chaldean order and by Jupiter under the triplicity scheme.
When would my progressed Sun reach Leo?
By the day for a year convention, after roughly two to three years of life. That technique carries its own assumptions and is not a statement about your birth chart.