Complex sentence: The four pillars are the year, month, day, and hour of one's birth, represented by two characters from the sexagenary cycle, one of the ten Celestial Stems and one of the twelve Earthly Branches.
Split into simpler sentences: The four pillars are the year, month, day, and hour of one's birth. Each pillar can be represented by two characters from the sexagenary cycle, one of the ten Celestial Stems and one of the twelve Earthly Branches.