When Is The Longest Day Of The Year 2024. Edt (2051 gmt), marking the longest day in the northern hemisphere. Thursday, june 20 is the official first day of northern astronomical summer for 2024 — summer solstice — which is the longest day of the year for this half of the planet.

This phenomenon occurs because during the solstice, the north pole is. For those living above the tropic of cancer, it is the longest day of the year.