Both. Since the Gregorian Calander didn't account for a leap day, January 20th is one of the few days that lands either at the end of Capricorn or at the beginning of Aquarius. I know this because I am a January 20th birthday and I find personal traits from both. I consider myself an Aquarius but I don't smack people around for calling me a Capricorn either.
Capricorn and Aquarius
The Zodiac sign Aquarius on the cusp of Capricorn.
December 22 - January 19 Capricorn January 20 - February 18 AquariusCapricorn up to the 19th, then Aquarius
The two signs that appear in the month of January are Capricorn and Aquarius.
January 1 to 19 is Capricorn, January 20 to 31 is Aquarius
If you were born on January 21st, you are on the cusp between Capricorn and Aquarius.
It depends on what your date of birth is. The two Sun signs in January are Capricorn and Aquarius.
Early January is capricorn until january 20. January 21 til' february 19 is aquarius.
Zodiac signs for January include the Capricorn which is from January the first to January the nineteenth. And also the Aquarius which is from January twentieth to January thirty-first.
Born 20th of January you are Aquarius on the cusp of Capricorn in the western zodiac and Otter in the Amerind earth magic zodiac.
Aquarius, on the cusp of Capricorn.