Longest Day Of Summer 2024. Is the solstice the longest day of the year?—and more! 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.

The summer solstice, marking the year’s longest daylight period, officially occurs thursday at 4:51 p.m. Is the solstice the longest day of the year?—and more!