How it is calculated
Capricorn crosses New Year, from 22 December to 19 January. The other signs sit inside one stretch of the calendar. The bounds match those usually printed with horoscopes, and they can differ by a couple of days from the constellations in the sky.
Sign = a month-and-day range from a fixed table
Where the numbers come from
- Date of birth
Example
10 August falls in Leo: the bounds on the screen run from 23 July to 22 August.
Questions
Why is the boundary disputed?
Different editions move the day where one sign meets the next. One widely printed set is used here, and it is written in the formula text on the page, after the result.
Is the year counted?
No. A sign needs only the day and the month.
Is this astronomy?
No. The constellations and the tropical signs do not match one for one.