When Is Summer Solstice 2024 What Time. This event marks the beginning of summer in astronomical terms and the longest day. In the southern hemisphere, it will occur on december 21 at 09:20 gmt (december 21, 04:20 a.m.
Read below to find out more. — the summer solstice — the exact moment when earth’s north pole is most tilted towards the sun — happens at 4:51 p.m.