Sun in Libra

The Sun defines the signs: its path through the sky is the ecliptic, and the twelve signs are twelve equal arcs of it, counted from the March equinox. The Sun enters a new sign roughly every thirty days; the four cardinal ingresses are the equinoxes and solstices. Your Sun sign is the sign it occupied when you were born, and the dates shift by a day between years, which is why boundary birthdays need the exact time.