Summer Solstice

The Summer Solstice is an event that is in, occurring in the player's town on the day that has the longest period of sunlight, usually June 21st. When the summer solstice occurs in Animal Crossing: New Leaf, the town holds a celebration, marked by a cut out board featuring a sun and a sunflower. If the player speaks with Isabelle who is located in the town plaza, she will give them a pair of Ladder Shades.

Real Life Definition
The summer solstice occurs when the tilt of a planet's semi-axis, in either the northern or the southern hemisphere, is most inclined toward the star (sun) that it orbits. Earth's maximum axial tilt toward the sun is 23° 26'. This happens twice each year, at which times the sun reaches its highest position in the sky as seen from the north or the south pole.