Indian astrology divides the sky by the Moon rather than the Sun: twenty-seven mansions of 13°20' each, one for roughly each day of the Moon's circuit of the stars.

Twelve signs is a solar scheme — it splits the year. Twenty-seven nakshatras split the sidereal month, which is 27.32 days, so the Moon spends about a day in each. Your nakshatra is the one the Moon was in when you were born, and in Indian practice it matters more than your Sun sign does; it decides the syllable a child may be named with, and it drives the dasha system that maps out a whole life.