1st Day Of Summer 2024 Uk Time. This is the longest day of the year and marks the start of summer in the northern hemisphere. Is it really the longest day of the year?
In 2024, it falls on june 20 and marks the sun’s northernmost point in the sky. The summer solstice in 2024 will be on thursday 20 june at 21.51 bst (20.51 gmt).