Which month is the north pole tilted directly toward the sun?

Winter in the Northern Hemisphere begins December 21 or 22, when the North Pole is tilted a full 23.5° away from the sun. This day is known as the winter solstice. The angle of the sun is the lowest and the Northern Hemisphere has the least amount of daylight.

there are so many examples for that in different areas, like biology experiment carried out in our lab recently.

here's one link: