In the northern hemisphere, the is on march 20th or 21st. vernal equinox summer solstice autumnal equinox winter solstice

Im pretty sure it's the vernal equinox in the northern hemisphere, and the autumnal equinox in the southern hemisphere.

Spring or vernal equinox on 20th march,

Explanation:

As the earth rotates on its axis of 23.4 degrees the relationship of the earth with its seasons and the patterns of the solar radiation tends to differ and this difference was observed form the north pole to the south pole. The obliquity of the elliptical shape of the earth makes the northern hemisphere inclined to the sun which has summer and the souther as winters thus the summer solstice occurs on the June 21 or 22nd. Similarity the winter solstice occurs in December when the earth moves towards to the sun in the southern hemisphere, and less of it in the north pr rays is less direct on the northern hemisphere. While march equinox is the same in all places as the onset of the summer solstice the vernal equinox takes place.

C14 hope it your welcome