The sun is overhead at the Tropic of Capricorn on December 22nd. The Tropic of Capricorn is a line of latitude located at 23.5 degrees south of the equator. On December 22nd, the sun is directly overhead at this line of latitude, meaning that the sun is at its highest point in the sky for the day.
It's important to note that the sun is overhead at the Tropic of Cancer, located at 23.5 degrees north of the equator, on June 21st each year. On this date, the sun is directly overhead at the Tropic of Cancer, marking the start of summer in the northern hemisphere and winter in the southern hemisphere.