When Is The Longest Day 2024. The longest day of the year, the summer solstice marks the official start of summer and is spiritually significant to many. (it can change a day from this date from year to year.) from then on, the days begin to get shorter, until we reach the shortest day of the year, the winter solstice.

The summer solstice, also known as the june solstice arrives june 20 at 4:51 p.m. Edt on june 20, according to timeanddate.com.