Answer: (1) Please mark the direction of the earth's revolution with arrows in the diagram. (2) Solar terms in the northern hemisphere when the earth revolves to point C..

(1) The revolution direction of the earth is from west to east (counterclockwise);

(2) It can be seen from the schematic diagram of the earth's revolution that when the earth is in position C, the latitude of direct sunlight is tropic of Capricorn, which is the winter solstice in the northern hemisphere, and the date is about 65438+February 22; When the earth revolves to point D, the direct latitude of the sun is the equator, that is, the vernal equinox in the northern hemisphere, and the date is around March 2 1;

(3) It can be seen from the schematic diagram of the earth's revolution that when the earth is in position A, the sun shines directly on the Tropic of Cancer, and when it is in position B, the latitude of direct sunlight is the equator. When the earth moves from point A to point B in orbit, the direct point of the sun moves from the Tropic of Cancer to the south, and the days and nights in the northern hemisphere are long. Xinyu City is located in the west of central Jiangxi Province and belongs to the northern hemisphere.

(4) Christmas is 65438+February 25th, which is closest to the winter solstice around 65438+February 22nd (when the earth is in position C, it is the winter solstice in the northern hemisphere).

So the answer is: (1); (2) Solstice in winter; 65438+February 22nd; Equator; (3) South; The days are long and the nights are short; (4)C。